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 A080121 #12 Jun 27 2021 11:54:44
%S A080121 1,1,2,1,1,2,1,2,1,5
%N A080121 a(n) is the smallest k > 0 such that n^2^k + (n+1)^2^k is prime, or -1 if no such k exists.
%C A080121 This sequence is the base-2 logarithm of A077659. It is known that a(11) > 22. Is it possible that 11^2^k + 12^2^k is composite for all k > 0?
%C A080121 The corresponding primes are listed in A122900. Currently a(n) is unknown for n in {11,15,18,20,28,44,46,49,51,52,53,55,57,58,61,62,64,71,73,77,81,83,91,92,94,...}. All n < 100 and 0 < k < 10 are checked. The first occurrence of each exponent k is listed in A122902. - _Alexander Adamchuk_, Sep 18 2006
%H A080121 T. D. Noe, <a href="http://www.sspectra.com/math/GenFermat11.txt">Factorizations of Generalized Fermat Numbers 12^2^k + 11^2^k</a>
%F A080121 If A058064(n) > 0, then a(n) = A058064(n). - _Max Alekseyev_, Sep 10 2020
%Y A080121 Cf. A058064, A057856, A077659, A122900, A122902.
%K A080121 hard,more,nonn
%O A080121 1,3
%A A080121 _T. D. Noe_, Jan 29 2003
%E A080121 Edited by _Max Alekseyev_, Sep 09 2020