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 A349266 #12 Oct 30 2024 12:16:19
%S A349266 1,8,64,904,15872,355688,9493504,296327464,10562158592,423645846728,
%T A349266 18878667833344,925434038426824,49488442978598912,2866986638191472168,
%U A349266 178867627497727197184,11956421282992330042984,852509723495811705208832,64584221654333725499376008
%N A349266 Generalized Euler numbers, a(n) = n!*[x^n](sec(7*x)*(-sin(2*x) + sin(4*x) + sin(6*x) + cos(x) + cos(3*x) - cos(5*x))).
%C A349266 For references and cross references, compare the overview in A349264.
%H A349266 Matthew House, <a href="/A349266/b349266.txt">Table of n, a(n) for n = 0..360</a>
%p A349266 sec(7*x)*(-sin(2*x) + sin(4*x) + sin(6*x) + cos(x) + cos(3*x) - cos(5*x)): series(%, x, 20): seq(n!*coeff(%, x, n), n = 0..17);
%t A349266 m = 17; CoefficientList[Series[Sec[7*x] * (-Sin[2*x] + Sin[4*x] + Sin[6*x] + Cos[x] + Cos[3*x] - Cos[5*x]), {x, 0, m}], x] * Range[0, m]! (* _Amiram Eldar_, Nov 21 2021 *)
%Y A349266 Row 7 of A349271.
%Y A349266 Bisections: A064068, A064072.
%Y A349266 Cf. A349264.
%K A349266 nonn
%O A349266 0,2
%A A349266 _Peter Luschny_, Nov 21 2021