This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A126856 #13 Feb 16 2025 08:33:04
%S A126856 109,461,1061,50777
%N A126856 Numbers n such that (31^n + 1)/32 is prime.
%C A126856 All terms are primes.
%C A126856 a(5) > 10^5. - _Robert Price_, Jul 12 2013
%H A126856 J. Brillhart et al., <a href="http://dx.doi.org/10.1090/conm/022">Factorizations of b^n +- 1</a>, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.
%H A126856 H. Dubner and T. Granlund, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL3/DUBNER/dubner.html">Primes of the Form (b^n+1)/(b+1)</a>, J. Integer Sequences, 3 (2000), #P00.2.7.
%H A126856 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Repunit.html">Repunit</a>.
%H A126856 H. Lifchitz, <a href="http://www.primenumbers.net/Henri/us/MersFermus.htm">Mersenne and Fermat primes field</a>
%t A126856 Do[ p=Prime[n]; If[ PrimeQ[ (31^p + 1)/32 ], Print[p] ], {n,1,1100} ]
%o A126856 (PARI) is(n)=isprime((31^n+1)/32) \\ _Charles R Greathouse IV_, Feb 17 2017
%Y A126856 Cf. A000978 = numbers n such that (2^n + 1)/3 is prime. Cf. A007658, A057171, A057172, A057173, A057175, A001562, A057177, A057178, A057179, A057180, A057181, A057182, A057183, A057184, A057185, A057186, A057187, A057188, A057189, A057190, A057191, A071380, A071381, A071382. Cf. A084741, A084742, A065507, A126659.
%K A126856 bref,hard,more,nonn
%O A126856 1,1
%A A126856 _Alexander Adamchuk_, Mar 23 2007
%E A126856 a(4) from _Robert Price_, Jul 12 2013