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 A028736 #27 Nov 24 2019 00:02:01 %S A028736 5,7,10,11,14,15,17,19,20,21,22 %N A028736 Nonsquares mod 23. %D A028736 Srinivasa Ramanujan, Collected Papers, Ed. G. H. Hardy et al., Cambridge 1927; Chelsea, NY, 1962. See "Congruence properties of partitions", p. 230. - _N. J. A. Sloane_, Jun 01 2014 %H A028736 George E. Andrews, James A. Sellers, <a href="http://arxiv.org/abs/1401.5345">Congruences for the Fishburn Numbers</a>, arXiv preprint arXiv:1401.5345 [math.NT], 2014. %e A028736 Since 11 is not a perfect square and there are no solutions to x^2 = 11 mod 23, 11 is in the sequence. %e A028736 Although 12 is not a perfect square either, there are solutions to x^2 = 12 mod 23, such as x = 9, x = 14. Thus 12 is not in the sequence. %t A028736 Select[Range[22], JacobiSymbol[#, 23] != 1 &] (* _Jean-François Alcover_, Oct 07 2018 *) %o A028736 (Scala) val squaresMod23 = (0 to 22).map(n => n * n).map(_ % 23) %o A028736 (0 to 22).diff(squaresMod23) // _Alonso del Arte_, Nov 23 2019 %Y A028736 Cf. A010385, A028759, A278579. %K A028736 nonn,fini,full %O A028736 1,1 %A A028736 _N. J. A. Sloane_