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 A245226 #36 May 17 2025 09:59:50
%S A245226 1,2,4,5,8,9,10,13,16,17,18,20,25,26,29,32,36,37,40,41,45,49,50,52,53,
%T A245226 58,61,64,65,68,72,73,74,80,81,82,85,89,90,97,98,100,101,104,106,109,
%U A245226 113,116,117,121,122,125,128,130,137,144,145,148,149,153,157
%N A245226 Values of n such that the equation x^2 - n*y^2 = n has integer solutions.
%C A245226 All the squares are in this sequence.
%C A245226 Differs from A001481 \ {0} and A248151 from a(17) = 36 on. The number 0 is in the sequence according to its definition. - _M. F. Hasler_, Oct 22 2019
%H A245226 Amiram Eldar, <a href="/A245226/b245226.txt">Table of n, a(n) for n = 1..10000</a>
%e A245226 5 is in the sequence because x^2-5*y^2=5 has integer solutions, including (x,y) = (5,2) and (85,38).
%t A245226 Select[Range[1,200],Solve[x^2==#*(1+y^2),{x,y},Integers]!={}&] (* _Vaclav Kotesovec_, Jul 15 2014 *)
%o A245226 (PARI) isok(m) = if (issquare(4*m), 1, #qfbsolve(Qfb(1, 0, -m), m, 2)); \\ _Michel Marcus_, May 17 2025
%Y A245226 Cf. A001481, A248151.
%K A245226 nonn
%O A245226 1,2
%A A245226 _Colin Barker_, Jul 14 2014