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 A340396 #18 Dec 22 2024 16:24:32
%S A340396 0,1,96,93789,1244160000,241885578271872,700566272328037500000,
%T A340396 30323548995402141685610526683,19627362048402730985830806120284160000,
%U A340396 189995156103157091521654945902925881881155376920,27506190205802587152768139358989866456457087869970721213256
%N A340396 a(n) = 2^(n^2 - 1) * Product_{j=1..n, k=1..n} (1 + sin(Pi*j/n)^2 + sin(Pi*k/n)^2).
%F A340396 a(n) = 2^(n^2-1) * Product_{j=1..n, k=1..n} (3 - cos(Pi*j/n)^2 - cos(Pi*k/n)^2).
%F A340396 a(n) = 2^(n^2-1) * Product_{j=1..n, k=1..n} (2-cos(2*Pi*j/n)/2-cos(2*Pi*k/n)/2).
%F A340396 a(n) ~ 2^(n^2-1) * exp(4*c*n^2/Pi^2), where c = Integral_{x=0..Pi/2, y=0..Pi/2} log(1 + sin(x)^2 + sin(y)^2) dy dx = -Pi^2*(log(2) + log(sqrt(2)-1)/2) + Pi * Integral_{x=0..Pi/2} log(1 + sqrt(1 + 1/(1 + sin(x)^2))) dx = A340421 = 1.627008991085721315763766677017604437985734719035793082916212355323520649...
%t A340396 Table[2^(n^2 - 1) * Product[1 + Sin[Pi*j/n]^2 + Sin[Pi*k/n]^2, {j, 1, n}, {k, 1, n}], {n, 0, 10}] // Round
%Y A340396 Cf. A004003, A007726, A065072, A067518, A127605, A340052, A340165, A340182, A340183, A340293.
%K A340396 nonn
%O A340396 0,3
%A A340396 _Vaclav Kotesovec_, Jan 06 2021