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 A335618 #11 Oct 02 2020 15:59:10
%S A335618 1,2,16,304,10496,568832,44486656,4742354944,660908343296,
%T A335618 116642430451712,25425572550148096,6708171660023824384,
%U A335618 2106760489114215120896,776654121137653931835392,332101031506139993274843136,163037618505293422657351450624,91075662529714266445615040823296
%N A335618 E.g.f.: Sum_{n>=0} Product_{k=1..n} tan(2*k*x).
%F A335618 a(n) ~ 2^(n - 1/2) * n!^2 / G^(n+1), where G is the Catalan constant A006752.
%F A335618 a(n) = 2^n * A177382(n).
%t A335618 nmax = 20; CoefficientList[Series[Sum[Product[Tan[2*k*x], {k, 1, n}], {n, 0, nmax}], {x, 0, nmax}], x] * Range[0, nmax]!
%Y A335618 Cf. A006752, A177382.
%K A335618 nonn
%O A335618 0,2
%A A335618 _Vaclav Kotesovec_, Oct 02 2020