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 A064071 #14 Feb 16 2025 08:32:45
%S A064071 2,158,79042,96448478,218987626882,798807132800798,
%T A064071 4273446686680147522,31521738825258026305118,
%U A064071 306606728264687314446344962,3802448636519829800140388609438
%N A064071 Generalized Euler number c(10,n).
%H A064071 Matthew House, <a href="/A064071/b064071.txt">Table of n, a(n) for n = 0..171</a>
%H A064071 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/EulerNumber.html">Euler Number</a>.
%H A064071 Daniel Shanks, <a href="https://doi.org/10.1090/S0025-5718-1967-0223295-5">Generalized Euler and class numbers</a>, Mathematics of Computation, Vol. 21, No. 100 (1967), pp. 689-694; <a href="https://doi.org/10.1090/S0025-5718-68-99652-X">Corrigenda</a>, ibid., Vol. 22, No. 103 (1968), p. 699.
%F A064071 a(n) = (2*n)!*[x^(2*n)](sec(10*x)*(cos(x) + cos(3*x) - cos(7*x) + cos(9*x))). - _Matthew House_, Oct 27 2024
%t A064071 Range[0, 18, 2]! CoefficientList[Series[Sec[10 x] (Cos[x] + Cos[3 x] - Cos[7 x] + Cos[9 x]), {x, 0, 18}], x^2] (* _Matthew House_, Oct 27 2024 *)
%Y A064071 Row 10 of A235605.
%K A064071 nonn,easy
%O A064071 0,1
%A A064071 _Eric W. Weisstein_, Aug 31 2001