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 A000604 M3419 N1383 #28 Sep 29 2019 13:06:18
%S A000604 1,4,11,29,54,99,163,239,344,486,648,847,1069,1355,1680,2046,2446,
%T A000604 2911,3443,4022,4662,5395,6145,6998,7913,8913,10006,11194,12437,13751,
%U A000604 15216,16710,18361,20123,21950,23919,25956,28150,30415,32876,35385,38049,40876
%N A000604 Number of nonnegative solutions to x^2 + y^2 + z^2 <= n^2.
%D A000604 H. Gupta, A Table of Values of N_3(t), Proc. National Institute of Sciences of India, 13 (1947), 35-63.
%D A000604 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D A000604 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A000604 T. D. Noe, <a href="/A000604/b000604.txt">Table of n, a(n) for n=0..500</a>
%F A000604 a(n) = [x^(n^2)] (1 + theta_3(x))^3/(8*(1 - x)), where theta_3() is the Jacobi theta function. - _Ilya Gutkovskiy_, Apr 15 2018
%t A000604 a[n_] := Sum[Boole[x^2 + y^2 + z^2 <= n^2], {x, 0, n}, {y, 0, Sqrt[n^2 - x^2]}, {z, 0, Sqrt[n^2 - x^2 - y^2]}]; A000604 = Table[an = a[n]; Print["a(", n, ") = ", an]; an, {n, 0, 100}] (* _Jean-François Alcover_, Feb 10 2016 *)
%Y A000604 Column k=3 of A302998.
%Y A000604 Cf. A000606.
%K A000604 nonn
%O A000604 0,2
%A A000604 _N. J. A. Sloane_
%E A000604 More terms from _David W. Wilson_, May 22 2000