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 A296740 #10 Dec 19 2017 16:23:12
%S A296740 1,1,17,481,26529,2355841,304490801,54346519137,12784369495873,
%T A296740 3834072115634689,1427927160049839185,646549058811594306017,
%U A296740 349778819738933516544737,222822626689237030117683841,165094750167986500169166495089,140768231241374238855897822250081
%N A296740 Expansion of e.g.f. sec(x*cosh(x)) (even powers only).
%F A296740 a(n) = (2*n)! * [x^(2*n)] sec(x*cosh(x)).
%e A296740 sec(x*cosh(x)) = 1 + x^2/2! + 17*x^4/4! + 481*x^6/6! + 26529*x^8/8! + ...
%t A296740 nmax = 15; Table[(CoefficientList[Series[Sec[x Cosh[x]], {x, 0, 2 nmax}], x] Range[0, 2 nmax]!)[[n]], {n, 1, 2 nmax + 1, 2}]
%o A296740 (PARI) first(n) = x='x+O('x^(2*n-2)); vecextract(Vec(serlaplace(1/cos(x*cosh(x)))), (4^n - 1)/3) \\ _Iain Fox_, Dec 19 2017
%Y A296740 Cf. A000364, A009008, A009009, A009010, A009011, A009015, A009016, A009446, A009447, A009633, A009634, A102072, A102075, A191512, A296728, A296729, A296730, A296731.
%K A296740 nonn
%O A296740 0,3
%A A296740 _Ilya Gutkovskiy_, Dec 19 2017