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 A296790 #8 Dec 21 2017 05:54:50
%S A296790 1,1,17,601,38849,4022641,609933521,127391254537,35067716300033,
%T A296790 12304447787106529,5360597104269331985,2839145693984474128057,
%U A296790 1796556232541725248396737,1338623568393194541863879761,1160057210771530210422755155409,1156898060700987368136296212581481
%N A296790 Expansion of e.g.f. sec(x*sec(x)) (even powers only).
%H A296790 Vaclav Kotesovec, <a href="/A296790/b296790.txt">Table of n, a(n) for n = 0..220</a>
%F A296790 a(n) = (2*n)! * [x^(2*n)] sec(x*sec(x)).
%F A296790 a(n) ~ c * d^n * n^(2*n + 1/2) / exp(2*n), where d = 4.5851486299312178337601256220116584724159... is the real root of the equation sqrt(d) * cos(2/sqrt(d)) = 4/Pi and c = 1.99453594228967461336... - _Vaclav Kotesovec_, Dec 21 2017
%e A296790 sec(x*sec(x)) = 1 + x^2/2! + 17*x^4/4! + 601*x^6/6! + 38849*x^8/8! + ...
%t A296790 nmax = 15; Table[(CoefficientList[Series[Sec[x Sec[x]], {x, 0, 2 nmax}], x] Range[0, 2 nmax]!)[[n]], {n, 1, 2 nmax + 1, 2}]
%Y A296790 Cf. A000364, A003712, A003718, A009008, A009009, A009010, A009011, A009015, A009118, A009562, A009765, A102072, A102075, A296731, A296740, A296791.
%K A296790 nonn
%O A296790 0,3
%A A296790 _Ilya Gutkovskiy_, Dec 20 2017