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 A337727 #8 Sep 17 2020 20:31:31
%S A337727 1,25,42001,498971881,21795091762081,2534333270094778681,
%T A337727 646315807872650838343345,317599587988620621961919733001,
%U A337727 274101148417699141578015206369183041,387502275541069630431671657548241448722521,849931991080760484603611346800010863970028660561
%N A337727 a(n) = (4*n)! * Sum_{k=0..n} 1 / (4*k)!.
%F A337727 E.g.f.: (1/2) * (cos(x) + cosh(x)) / (1 - x^4) = 1 + 25*x^4/4! + 42001*x^8/8! + 498971881*x^12/12! + ...
%F A337727 a(n) = floor(c * (4*n)!), where c = (cos(1) + cosh(1)) / 2 = A332890.
%t A337727 Table[(4 n)! Sum[1/(4 k)!, {k, 0, n}], {n, 0, 10}]
%t A337727 Table[(4 n)! SeriesCoefficient[(1/2) (Cos[x] + Cosh[x])/(1 - x^4), {x, 0, 4 n}], {n, 0, 10}]
%t A337727 Table[Floor[(1/2) (Cos[1] + Cosh[1]) (4 n)!], {n, 0, 10}]
%o A337727 (PARI) a(n) = (4*n)!*sum(k=0, n, 1/(4*k)!); \\ _Michel Marcus_, Sep 17 2020
%Y A337727 Cf. A000522, A051396, A051397, A087350, A100733, A330045, A332890, A337725, A337726, A337728, A337729, A337730.
%K A337727 nonn
%O A337727 0,2
%A A337727 _Ilya Gutkovskiy_, Sep 17 2020