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A128847 Denominators of the continued fraction convergents of the decimal concatenation of the upper bounds of twin primes. 0

%I

%S 1,1,2,7,1304,1311,2615,139906,142521,424948,1417365,1842313,3259678,

%T 50737483,53997161,320723288,374720449,2569045982,100567513747,

%U 3603437154114739,3603537721628486,54052965256913543,273868364006196201

%N Denominators of the continued fraction convergents of the decimal concatenation of the upper bounds of twin primes.

%F The upper bounds of twin primes 5,7,13,19... are concatenated and then preceded by a decimal point to create the fraction N = .57131931... . This number is then evaluated with n=0,m=steps to iterate,x = N, a(0)=floor(N) using the loop: do a(n)=floor(x) x=1/(x-a(n)) n=n+1 loop until n=m

%o (PARI) cattwinsU(n) = { a=".";forprime(x=3,n,if(ispseudoprime(x+2),a=concat(a,Str(x+2))));a=eval(a) } cfrac2(m,f) = { default(realprecision,1000); cf = vector(m+10); cf = contfrac(f); for(m1=1,m-1, r=cf[m1+1]; forstep(n=m1,1,-1, r = 1/r; r+=cf[n];); numer=numerator(r); denom=denominator(r); print1(denom","); ) }

%K frac,nonn,base

%O 0,3

%A _Cino Hilliard_, Apr 16 2007

%E Edited by _Charles R Greathouse IV_, Apr 25 2010

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Last modified August 5 07:29 EDT 2020. Contains 336209 sequences. (Running on oeis4.)