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 A341535 #27 Feb 28 2023 23:48:23
%S A341535 1,2,36,224,38416,2540032,4115479104,3044533460992,48656376372265216,
%T A341535 387018647188487143424,62441634466575620320306176,
%U A341535 5221063878050546380074377019392,8590392749565593082105293619707908096,7476351474500749779460880888573410601336832
%N A341535 a(n) = sqrt(Product_{1<=j,k<=n} (4*sin((2*j-1)*Pi/(2*n))^2 + 4*sin((2*k-1)*Pi/n)^2)).
%H A341535 Seiichi Manyama, <a href="/A341535/b341535.txt">Table of n, a(n) for n = 0..62</a>
%F A341535 a(n) ~ 2^(1/4)*(1 + sqrt(2)*(1 + (-1)^n)/2) * exp(2*G*n^2/Pi), where G is Catalan's constant A006752. - _Vaclav Kotesovec_, Feb 14 2021
%F A341535 If n is odd, a(n) = 2*A341478(n). - _Seiichi Manyama_, Feb 19 2021
%t A341535 Table[Sqrt[Product[4*Sin[(2*j - 1)*Pi/(2*n)]^2 + 4*Sin[(2*k - 1)*Pi/n]^2, {k, 1, n}, {j, 1, n}]], {n, 0, 20}] // Round (* _Vaclav Kotesovec_, Feb 14 2021 *)
%o A341535 (PARI) default(realprecision, 120);
%o A341535 a(n) = round(sqrt(prod(j=1, n, prod(k=1, n, 4*sin((2*j-1)*Pi/(2*n))^2+4*sin((2*k-1)*Pi/n)^2))));
%Y A341535 Main diagonal of A341533.
%Y A341535 Cf. A341478, A341479, A341782.
%K A341535 nonn
%O A341535 0,2
%A A341535 _Seiichi Manyama_, Feb 13 2021