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 A341402 #6 Feb 10 2021 20:43:26
%S A341402 1,8,29,64,106,169,281,422,548,702,961,1276,1556,1864,2326,2893,3390,
%T A341402 3852,4545,5455,6253,7002,8080,9361,10453,11496,12903,14618,16194,
%U A341402 17643,19589,22011,24027,25714,28143,31188,33792,36137,39203,42920,46294,49108,52580,57165,61365
%N A341402 Number of nonnegative solutions to (x_1)^2 + (x_2)^2 + ... + (x_7)^2 <= n.
%C A341402 Partial sums of A045849.
%H A341402 <a href="/index/Su#ssq">Index entries for sequences related to sums of squares</a>
%F A341402 G.f.: (1 + theta_3(x))^7 / (128 * (1 - x)).
%F A341402 a(n^2) = A055406(n).
%p A341402 b:= proc(n, k) option remember; `if`(n=0, 1, `if`(n<0 or k<1, 0,
%p A341402 b(n, k-1)+add(b(n-j^2, k-1), j=1..isqrt(n))))
%p A341402 end:
%p A341402 a:= proc(n) option remember; b(n, 7)+`if`(n>0, a(n-1), 0) end:
%p A341402 seq(a(n), n=0..44); # _Alois P. Heinz_, Feb 10 2021
%t A341402 nmax = 44; CoefficientList[Series[(1 + EllipticTheta[3, 0, x])^7/(128 (1 - x)), {x, 0, nmax}], x]
%Y A341402 Cf. A000122, A000606, A003059, A045849, A055406, A055413, A224212, A224213, A302862, A341400, A341401.
%K A341402 nonn
%O A341402 0,2
%A A341402 _Ilya Gutkovskiy_, Feb 10 2021