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 A321394 #10 Aug 19 2021 11:04:05
%S A321394 1,1,2,10,75,816,11407,194480,3871075,87700736,2220246387,62010892800,
%T A321394 1892138207375,62591994720256,2230631475837767,85188256574494720,
%U A321394 3470563987113896475,150234341045137637376,6886077311552162511547,333165973379285030666240,16967906593223743786978375
%N A321394 a(n) = (1/24)*n!*[x^n] (9 + sectan(4*x) + 6*sectan(2*x) + 8*sectan(x)) where sectan(x) = sec(x) + tan(x).
%C A321394 See A320956 for motivation and definitions.
%p A321394 sectan := x -> sec(x) + tan(x): # sin(Pi/4 + x/2)*csc(Pi/4 - x/2)
%p A321394 egf := 9 + sectan(4*x) + 6*sectan(2*x) + 8*sectan(x):
%p A321394 ser := series(egf, x, 22): seq((1/24)*n!*coeff(ser, x, n), n=0..20);
%t A321394 m = 20;
%t A321394 sectan[x_] := Sec[x] + Tan[x];
%t A321394 egf = 9 + sectan[4x] + 6 sectan[2x] + 8 sectan[x];
%t A321394 (1/24) CoefficientList[egf + O[x]^(m+1), x] Range[0, m]! (* _Jean-François Alcover_, Aug 19 2021 *)
%o A321394 (PARI) sectan(x) = 1/cos(x) + tan(x);
%o A321394 my(x='x+O('x^25)); Vec(serlaplace(9 + sectan(4*x) + 6*sectan(2*x) + 8*sectan(x)))/24 \\ _Michel Marcus_, Aug 19 2021
%Y A321394 Cf. A000111 (n=1), A000828 (n=2), A320957 (n=3), this sequence (n=4), A320956.
%K A321394 nonn
%O A321394 0,3
%A A321394 _Peter Luschny_, Nov 08 2018