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 A363780 #11 Jun 22 2023 07:22:01
%S A363780 1,-1,3,-10,31,-96,294,-876,2511,-6796,16698,-33540,31174,184534,
%T A363780 -1627812,8912760,-41466433,176963760,-714194382,2766892840,
%U A363780 -10374065814,37815483948,-134334781732,465432203640,-1571910265770,5164302815179,-16438631981418
%N A363780 a(n) = [x^n] 1/(Sum_{k>=0} x^(k^2))^n.
%Y A363780 Main diagonal of A363778.
%Y A363780 Cf. A287617.
%K A363780 sign
%O A363780 0,3
%A A363780 _Seiichi Manyama_, Jun 21 2023