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A086397 Numerators of the rational convergents to sqrt(2) if both numerators and denominators are primes. 4
3, 7, 41, 63018038201, 19175002942688032928599 (list; graph; refs; listen; history; text; internal format)



Next term, if it exists, is bigger than 489 digits (the 1279th convergent to sqrt(2)). - Joshua Zucker, May 08 2006

Are the terms >= 7 the primes in A183064? Is this a subsequence of A088165? - R. J. Mathar, Aug 16 2019


Table of n, a(n) for n=1..5.

Andrej Dujella, Mirela Jukić Bokun, Ivan Soldo, A Pellian equation with primes and applications to D(-1)-quadruples, arXiv:1706.01959 [math.NT], 2017.


For[n = 2, n < 1500, n++, a := Join[{1}, Table[2, {i, 2, n}]]; If[PrimeQ[Denominator[FromContinuedFraction[a]]], If[PrimeQ[Numerator[FromContinuedFraction[a]]], Print[Numerator[FromContinuedFraction[a]]]]]] (* Stefan Steinerberger, May 09 2006 *)


(PARI) cfracnumdenomprime(m, f) = { default(realprecision, 3000); cf = vector(m+10); x=f; for(n=0, m, i=floor(x); x=1/(x-i); cf[n+1] = i; ); for(m1=0, m, r=cf[m1+1]; forstep(n=m1, 1, -1, r = 1/r; r+=cf[n]; ); numer=numerator(r); denom=denominator(r); if(ispseudoprime(numer)&&ispseudoprime(denom), print1(numer", "); numer2=numer; denom2=denom); ) default(realprecision, 28); }


Denominators are A118612.

Sequence in context: A181148 A179907 A080581 * A229941 A019018 A018993

Adjacent sequences:  A086394 A086395 A086396 * A086398 A086399 A086400




Cino Hilliard, Sep 06 2003


More terms from Cino Hilliard, Jan 15 2005

Edited by N. J. A. Sloane, Aug 06 2009 at the suggestion of R. J. Mathar



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Last modified December 9 03:27 EST 2019. Contains 329872 sequences. (Running on oeis4.)