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 A229296 #14 Aug 07 2018 17:50:57
%S A229296 2,4,2,8,18,4,2,16,18,36,2,8,50,4,18,32,66,36,2,72,2,4,2,16,130,100,
%T A229296 18,8,114,36,2,64,2,132,18,72,146,4,50,144,162,4,2,8,162,4,2,32,98,
%U A229296 260,66,200,210,36,18,16,2,228,2,72,242,4,18,128,450,4,2
%N A229296 Number of solutions to x^2 + y^2 == n (mod 2*n) for x,y in [0, 2*n).
%H A229296 Andrew Howroyd, <a href="/A229296/b229296.txt">Table of n, a(n) for n = 1..1000</a>
%F A229296 a(n) = 2*A086933(n). - _Andrew Howroyd_, Aug 07 2018
%t A229296 A[n_] := Sum[If[Mod[a^2+b^2, 2n] == n, 1, 0], {a, 0, 2n - 1}, {b, 0, 2n - 1}]; Array[A, 100]
%o A229296 (PARI) a(n)={my(m=2*n); my(p=Mod(sum(i=0, m-1, x^(i^2%m)), x^m-1)^2); polcoeff( lift(p), n)} \\ _Andrew Howroyd_, Aug 07 2018
%Y A229296 Cf. A086933, A229294, A229295, A229296, A229297.
%K A229296 nonn
%O A229296 1,1
%A A229296 _José María Grau Ribas_, Sep 22 2013