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 A274971 #27 Jul 08 2023 21:01:42
%S A274971 1,7,19,31,37,43,61,67,79,91,103,127,139,151,157,163,169,199,211,217,
%T A274971 223,247,271,283,307,313,331,343,349,367,373,379,397,403,427,439,463,
%U A274971 469,487,499,511,523,547,553,571,577,607,613,619,631,643,661,679,691
%N A274971 Numbers k such that (x+1)^3 - x^3 = k*y^2 has integer solutions.
%H A274971 Ray Chandler, <a href="/A274971/b274971.txt">Table of n, a(n) for n = 1..10000</a>
%H A274971 Dario A. Alpern, <a href="https://www.alpertron.com.ar/QUAD.HTM">Quadratic two integer variable equation solver</a>
%e A274971 7 is in the sequence because, for instance, (167^3-166^3)/7 = 11881 = 109^2.
%t A274971 A004611=Select[Range[500],And@@(Mod[#,3]==1&)/@(First/@FactorInteger[#])&]; Select[A004611,Reduce[x^2+3== 12*#*y^2,{x,y},Integers]=!=False &] (* _Ray Chandler_, Jul 24 2016 *)
%Y A274971 Cf. A001921 (k=1), A144929 (k=7), A145124 (k=19), A145323 (k=31), A145700 (k=37), A145336 (k=43), A274972 (k=61), A145212 (k=67), A145309 (k=79), A145530 (k=91), A147530 (k=103), A145720 (k=127).
%Y A274971 Cf. A003215 is a subsequence; A004611 contains this sequence.
%K A274971 nonn
%O A274971 1,2
%A A274971 _Colin Barker_, Jul 13 2016
%E A274971 More terms using solver at Alpern link by _Ray Chandler_, Jul 23 2016