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 A302995 #6 Feb 16 2025 08:33:53
%S A302995 1,1,1,7,32,177,1269,9263,74452,652710,6078048,60447082,631870024,
%T A302995 6915613084,79113376037,941759419159,11630647314564,148799595377384,
%U A302995 1966441829785081,26793749867965515,375812005722920406,5416574818546042067,80123280319100908258,1214860029446181979357
%N A302995 a(n) = [x^(n^2)] (theta_3(x) - 1)^n/(2^n*(1 - x)), where theta_3() is the Jacobi theta function.
%C A302995 a(n) = number of positive solutions to (x_1)^2 + (x_2)^2 + ... + (x_n)^2 <= n^2.
%H A302995 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/JacobiThetaFunctions.html">Jacobi Theta Functions</a>
%H A302995 <a href="/index/Su#ssq">Index entries for sequences related to sums of squares</a>
%t A302995 Table[SeriesCoefficient[(EllipticTheta[3, 0, x] - 1)^n/(2^n (1 - x)), {x, 0, n^2}], {n, 0, 23}]
%t A302995 Join[{1}, Table[SeriesCoefficient[1/(1 - x) Sum[x^k^2, {k, 1, n}]^n, {x, 0, n^2}], {n, 23}]]
%Y A302995 Cf. A000122, A001182, A253663, A298330, A302861, A302863.
%K A302995 nonn
%O A302995 0,4
%A A302995 _Ilya Gutkovskiy_, Apr 17 2018