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 A305710 #6 Mar 27 2019 03:53:06
%S A305710 1,1,3,11,53,297,1959,14499,120409,1097025,10931771,117685163,
%T A305710 1363889133,16887554569,222672557631,3110742121059,45912214062961,
%U A305710 713290136581697,11636755988405555,198800967493444875,3549276499518132325,66076184834921382313,1280502976522048458647
%N A305710 Expansion of e.g.f. exp(sec(x)*exp(x) - 1).
%e A305710 exp(sec(x)*exp(x) - 1) = 1 + x + 3*x^2/2! + 11*x^3/3! + 53*x^4/4! + 297*x^5/5! + 1959*x^6/6! + 14499*x^7/7! + ...
%p A305710 a:=series(exp(sec(x)*exp(x)-1),x=0,23): seq(n!*coeff(a,x,n),n=0..22); # _Paolo P. Lava_, Mar 26 2019
%t A305710 nmax = 22; CoefficientList[Series[Exp[Sec[x] Exp[x] - 1], {x, 0, nmax}], x] Range[0, nmax]!
%t A305710 a[n_] := a[n] = Sum[(2 I)^k EulerE[k, 1/2 - I/2] Binomial[n - 1, k - 1] a[n - k], {k, 1, n}]; a[0] = 1; Table[a[n], {n, 0, 22}]
%Y A305710 Cf. A000364, A003701, A004211, A009006, A009212, A009248, A009268, A305708.
%K A305710 nonn
%O A305710 0,3
%A A305710 _Ilya Gutkovskiy_, Jun 08 2018