Chapter 13

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609886913128081573442101642685834146932480595852486941819774796907287883592668 681656295544982771231241739359880261799888459616178511015265142019295770748553 621477960335310125476008798159293638317998764183171554007533292685532366426931 296113029111025520184013514875239936403973082905020852634097000954786673108797 194683512466021134551718490623186005559263054213445514986015560105003175358818 729120260192377759863996689880745305394749277211166300200942565181578057244342 364079464408162259363253332269243879958128832143605562042103400838175855005147 159035775759548082123045351970406460845175874648068200206983521552062681616351 546128866398014618829887276854773455787107021211539099616380870095321225622743 875843134805266684710810680269730212282707006426650390681672492836820335198867 111490598052146276725080070297023977357726727420363586882813118327458332011650 300663287203505391842923422615658023387724025020112031995598518110930146011943 357535550858470014843437983175002044765810711671261397841703350673509295101418 035838107387174672478179790404106522129323473426130545413167650437830630173033 609770202799206445648799740500038602872011502383662940004575718574473772243957 859564732954178543698075776889882013103418542402303648469135979284487987981305 207957632878889539116749028392001145076602606946768688776828321352341343714498 172069787183303687222279154323894660649265107409869767073908525830747627588164 599684978287226131955625954677069349468340871546911321236846310103649548391557 706597324218895772995796196414385734757463701320460682282702082229074510097287 470965263450130698632304053253571980160303875529709389914239699309762498208260 656985764679971094870832353759361789431473305428008521443480289919702645320371 540591669433894078131793357800419838012267461497196943352987715772147171547862 923549410773155563038338703393228578903032372374987517727227965664327459492466 828637381314870736911784345741891568168064181395191242008190333580358992436427 792146567461304662028297877682556837732219391714165673332227709019541094949164 731317250808556100846480973008466031051651987243311582800178339090672155044828 435337148282908872278634250781579720625368059903173644323312066359683471335647 572519875946415674309642065162759421558450733571189718736416717232624102189802 986643530813745547079843131265127944488423520875100157013114234552402349201621 895330336887481355125635530103043133142183302509644544691916000304561434594091 842118084695176156346518430689840576347349894596331764219496350825991275112646 178968314081728405445653705633918909972488638272414746021940065089177324960678 701639578875389300114821175213799849881345936920742369738692578177604561048165 791951728359470764717852032653804264508712488409275144263817247478872455521125 122686157803180905175243587957901639589918375503356805003310878302478688338855 646264365123996336007949820946888100805705914494984147795125582819571118249753 142501534840648675362586395929915055763877114942594265588179739300156153186304 918492515415542607279787417977785786967831684043241053939562352551581578479080 217437441480744707729267778098749964843897754964276371179512590516188343080479 627627215997745371033986957853630712266447521404867551898386833006795876131353 061615629472534881740658887722803330178811024150345211269474743386476066285988 462296383533038290827914933752828644732943045951482219064252892987971875320122 303106072804280427262462568416437742171936686010084615581521635282403006879396 842836076754390842203901164603231158190564588614887636276553758069184106730228 889992731281104098031581800960316548425810811583034173443155831075066192714369 565224756157760818281064759373776548828531997751494021282367027889259567476651 994432153571589252600399312123424069148817040108814852822860658109915341468231 434111113996190820817658629913660653985709633814345784059091998325755015350541 335156433200795915635980201946177034129575229788245918427630740173255464494827 998091485820424906785146136481107013187529775997375080905292723700988248579688 317119428485099110702270510482145419412443049360943824740041797224596723946566 554038885

sum(1/binomial(2*n,n),n=1..infinity) to 1024 digits.

0.7363998587187150779097951683649234960631258329094979056821966523 0847181802807864081869444182490225974582720321801478346017690055 4229868477732944895880680415915142979334394163998909738083425408 1520029546146727664979554751571056972458855740951911198864857982 9433328581834861487045790649324680582119729407417116198674601654 4485479889543142786974292724928598532747380156659130512545236749 4154597773449101860414448973793322220865507304585980050655111918 9338017331890327068185957293937796352569292021414362805981608876 3091647656764089200563681690417652792652154091682197250552326447 7646813159383043809989583900078755611335395490521438524130346215 3457599854790211802421898533425927038158436578567901788663851909 9589847649578146455045212664074436825052408587935995452420291968 6774100311819740383505356065846433687090253752952485814436801506 6642240052190351749758439051568244234310796570611672868391753708 6438175031998334537917178650178729583132166807457526236785528510 1696922360975795282761033968077326069723073543573616136752770598

sum(1/(n*binomial(2*n,n)),,n=1..infinity); to 1024 digits.

0.6045997880780726168646927525473852440946887493642468585232949784 6270772704211796122804166273735338961874080482702217519026535083 1344802716599417343821020623872714469001591245998364607125138112 2280044319220091497469332127356585458688283611427866798297286974 4149992872752292230568685973987020873179594111125674298011902481 6728219834314714180461439087392897799121070234988695768817855124 1231896660173652790621673460689983331298260956878970075982667878 4007025997835490602278935940906694528853938032121544208972413314 4637471485146133800845522535626479188978231137523295875828489671 6470219739074565714984375850118133417003093235782157786195519323 0186399782185317703632847800138890557237654867851852682995777864 9384771474367219682567818996111655237578612881903993178630437953 0161150467729610575258034098769650530635380629428728721655202259 9963360078285527624637658577352366351466194855917509302587630562 9657262547997501806875767975268094374698250211186289355178292765 2545383541463692924141550952115989104584610315360424205129155898

sum(1/n^n,n=1..infinity); to 1024 places.

1.291285997062663540407282590595600541498619368274522317310002445 1369445387652344555588170411294297089849950709248154305484104874 1928486419757916355594791369649697415687802079972917794827300902 5649230550720966638128467012053685745978703001277894129288253551 7702223833753193457492599677796483008495491110669649755010519757 4291162109702156166953289768924278900580939081478809403679930558 9535200633716110465094638606808864998606531021853412479159737305 2710686824652246770336860469870234201965831431339687388172956893 5536851798521420666264165438061224569940966356043885239969381304 4840101532338556989547899226146597068180753342912289091004995136 4103584723741679660994037428872280908239472403012423375069665874 3147683502983470096596930198071220594154742391888495488920431478 4037389693592832744937301860181757952468190913559650620576842700 8907326547137233834847185623248044173423385652705113744822086069 8381169706447896315548031108686846807807010570342300009547766282 9927022264266182213029160934485049255679995121281765081062180734

The Traveling Salesman Constant, conjectured to be is equal to 4/153*(1+2*sqrt(2))*sqrt(51) to 1000 digits.

.71478270079129427201898487962108409673134559709443031939645700411546117738335\ 879706770213413096294533561547227555717895434127457058654186783324525211448435\ 423370160734747472156550615029635220251467885538763575736849440141040232425552\ 364704664879061099570515393895856312208463669793487083110116620844381148478166\ 953397235099760820248716126335472464734965931893615249427223312525010786175723\ 903850094286618856777573472030439593602004416562703436281430743460123517870481\ 605658651710683396096658326275655282564938079930443149087689479702230621110332\ 425071472991466740480185001283536160284031917506648494911514005453049419741227\ 682161417117934301981301137112382110439175900888848785626934265741110708345544\ 731999904108101036079296059394893034776038533840976912765053467151339515952296\ 425034733122079333744376059531233173573812633038639781766805813536012423214277\ 007401299039458343003042376467569131088941308597225474822014342730622766746260\ 22472480156659330677754354367566446245619515011589704068286465445

The Tribonacci constant, is such that 1/(1-x-x^2-x^3) once expanded into a series will give coefficients proportional to approx. c**n and c = (to 1000 digits).

1.8392867552141611325518525646532866004241787460975922467787586394042032220819\ 664257384354194283070141419798268592409741641784507465074369438315458204995137\ 962496555396446136661215402779726781189410412116092232821559560718167121823659\ 866522733785378156969892521173957914132287210618789840852549569311453491349853\ 459576175035965221323814247272722417358187700069790551025490449657107425265477\ 228110065989375556363093330528262357538519719942991453008254663977472900587005\ 974481391931672825848839626332970700687236831127837750250557122275153259578946\ 560570686422283918659698294691356239220443192476147068811451726766712743964146\ 212571843342662340390218352494591033227231061513286997030808036302223324997105\ 243107472354231399744381826565607351940357874911762680524537079221110849710806\ 876410050156541475662235008885665949715821834184868714802901255436993480513679\ 165025853053878276666126224317766358200942985505387325991651787730184472388604\ 26222324857820792721049160181783725613203439814302274533997621231

/ 19 1/2\1/3 4 |---- + 1/9 33 | + ----------------------- + 1/3 \ 27 / / 19 1/2\1/3 9 |---- + 1/9 33 | \ 27 /

in fact the n'th Tribonacci number is given by this EXACT formula. ---------------------------------------------------------------------

See : http://www.labri.u-bordeaux.fr/~loeb/book/92pl.html

Comment calculer le nieme nombre de Tribonacci

Resume of a conference given in 1993 (Universite Bordeaux I, LaBRI).

1/2 1/3 1/2 1/3 n 1/2 1/3 (1/3 (19 + 3 33 ) + 1/3 (19 - 3 33 ) + 1/3) (586 + 102 33 ) 3 --------------------------------------------------------------------------- 1/2 2/3 1/2 1/3 (586 + 102 33 ) + 4 - 2 (586 + 102 33 )

To get the actual n'th Tribonacci number just round the result to the nearest integer.

Here is the formula 'lprinted'...

3*(1/3*(19+3*33^(1/2))^(1/3)+1/3*(19-3*33^(1/2))^(1/3)+1/3)^n/((586+102*33^(1 /2))^(2/3)+4-2*(586+102*33^(1/2))^(1/3))*(586+102*33^(1/2))^(1/3);

This formula has 2 parts, first the numerator is the root of (x^3-x^2-x-1) no surprise here, but the denominator was obtained using LLL (Pari-Gp) algorithm. The thing is, if you try to get a closed formula by doing the Z-transform or anything classical, it won't work very well since the actual symbolic expression will be huge and won't simplify.

The numerical values of Tribonacci numbers are c**n essentially and the c here is one of the roots of (x^3-x^2-x-1), then there is another constant c2. So the exact formula is c**n/c2.

Another way of doing 'exact formulas' are given by using [ ] function the n'th term of the series expansion of 1/(1+x+x**2) is

1 - 2 floor(1/3 n + 2/3) + floor(1/3 n + 1/3) + floor(1/3 n)

The twin primes constant.

0.660161815846869573927812110014555778432623

The Varga constant, also known to be the 1/(one-ninth constant).

9.2890254919208189187554494359517450610317

One-ninth constant is 0.1076539192264845766153234450909471905879765038

0.4749493799879206503325046363279829685595493732172029822833310248 6455792917488386027427564125050214441890378494262395464775250455 2099778523950882780814821592082565202912193041770281959987798787 6404342380353179170625016170252803841553681975679189489592083858

to 256 digits is also this closed expression.

2**(5/4)*sqrt(Pi)*exp(Pi/8)*GAMMA(1/4)**(-2);

-Zeta(1,1/2).

is also equal to -Zeta(1/2)*(1/2*gamma+1/2*ln(8*Pi)+1/4*Pi).

3.922646139209151727471531446714599513730323971506505209568298485 2547208031503382848806505231041456914038034379886764996843321856 0187370796648866325531877003002927708284792679262934379740474743 4560678349258709176744625306684542186046544092107149397014020908

-Zeta(-1/2) to 256 digits.

0.2078862249773545660173067253970493022262685312876725376101135571 0614729193229234048754326694073321564310997561412868956566132691 4694458311965705623294109531061640017807007041375078320755666248 7877869206615046914282912338325693716136777293836109459387888090

Zeta(2) or Pi**2/6 to 10000 places.