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 A126915 #15 Sep 08 2022 08:45:29
%S A126915 2,6,12,60,68,138,270,446,488,620,656,798,872,942,950,1136,1140,1256,
%T A126915 1400,1418,1506,1638,1776,1922,1992,2070,2082,2096,2220,2346,2462,
%U A126915 2580,2606,2916
%N A126915 Numbers k such that 1 + k^2 + k^4 + k^6 + k^8 + k^10 + k^12 + k^14 + k^16 + k^18 + k^20 + k^21 is prime.
%H A126915 Daniel Starodubtsev, <a href="/A126915/b126915.txt">Table of n, a(n) for n = 1..10000</a>
%t A126915 a = {}; Do[If[PrimeQ[1 + n^2 + n^4 + n^6 + n^8 + n^10 + n^12 + n^14 + n^16 + n^18 + n^20 + n^21], AppendTo[a, n]], {n, 1, 1400}]; a
%o A126915 (PARI) is(n)=isprime(1+n^2+n^4+n^6+n^8+n^10+n^12+n^14+n^16+n^18+n^20+n^21) \\ _Charles R Greathouse IV_, Jun 13 2017
%o A126915 (Magma) [k:k in [1..3000]| IsPrime(1+k^2+k^4+k^6+k^8+k^10+k^12+k^14+k^16+ k^18+k^20 +k^21)]; // _Marius A. Burtea_, Feb 11 2020
%Y A126915 Cf. A049407, A124175 A124176 A124177, A124178, A124179, A124180, A124181, A126908-A126916.
%K A126915 nonn,easy
%O A126915 1,1
%A A126915 _Artur Jasinski_, Dec 31 2006