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 A117437 #13 Sep 08 2022 08:45:24
%S A117437 1,1,5,13,105,441,5165,30213,469585,3529201,68525525,629401213,
%T A117437 14664091065,159175688361,4326609913085,54189700721013,
%U A117437 1683369010256545,23894940183997921,835066388382183845,13248060325188261613
%N A117437 Expansion of e.g.f.: exp(x)*sec(2*x).
%C A117437 Row sums of A117436.
%C A117437 Binomial transform of A002436 (with interpolated zeros).
%H A117437 G. C. Greubel, <a href="/A117437/b117437.txt">Table of n, a(n) for n = 0..425</a>
%F A117437 a(n) ~ n! * 2^(2*n+1) * (exp(Pi/4) + (-1)^n*exp(-Pi/4)) / Pi^(n+1). - _Vaclav Kotesovec_, Aug 04 2014
%t A117437 With[{nn=30},CoefficientList[Series[Exp[x]Sec[2x],{x,0,nn}],x] Range[0,nn]!] (* _Harvey P. Dale_, Dec 13 2011 *)
%o A117437 (Magma) R<x>:=PowerSeriesRing(Rationals(), 30); Coefficients(R!(Laplace( Exp(x)*Sec(2*x) ))); // _G. C. Greubel_, May 31 2021
%o A117437 (Sage) [factorial(n)*( exp(x)*sec(2*x) ).series(x,n+1).list()[n] for n in (0..30)] # _G. C. Greubel_, May 31 2021
%o A117437 (PARI) my(x='x+O('x^30)); Vec(serlaplace(exp(x)/cos(2*x))) \\ _Michel Marcus_, Jun 01 2021
%Y A117437 Cf. A002436, A117436.
%K A117437 easy,nonn
%O A117437 0,3
%A A117437 _Paul Barry_, Mar 16 2006