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 A203677 #10 Sep 08 2023 09:06:01
%S A203677 1,17,135218,3185418047264,795022479172023183220864,
%T A203677 5554004683279652358469137440150614769664,
%U A203677 2378852972988348412358457063032448409092378064835941488918528
%N A203677 Vandermonde sequence using x^2 + y^2 applied to (1,4,9,...,n^2).
%C A203677 See A093883 for a discussion and guide to related sequences.
%F A203677 a(n) ~ c * 2^(n^2/2 - 1) * (1 + sqrt(2))^(n*(n+1)/sqrt(2)) * exp((Pi/2^(3/2) - 3)*n^2 + (Pi/2^(3/2) + 2)*n) * n^(2*n^2 - 2*n - 3/2), where c = 0.154147406559582639039828423669556073435424655001221440918550218582474208... - _Vaclav Kotesovec_, Sep 08 2023
%t A203677 f[j_] := j^2; z = 12;
%t A203677 u[n_] := Product[f[j]^2 + f[k]^2, {j, 1, k - 1}]
%t A203677 v[n_] := Product[u[n], {k, 2, n}]
%t A203677 Table[v[n], {n, 1, z}] (* A203677 *)
%t A203677 Table[v[n + 1]/v[n], {n, 1, z}] (* A203678 *)
%Y A203677 Cf. A324437.
%K A203677 nonn
%O A203677 1,2
%A A203677 _Clark Kimberling_, Jan 04 2012