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 A064074 #21 Feb 16 2025 08:32:45 %S A064074 12,2160,1415232,1951153920,4611775398912,16653520425185280, %T A064074 85285640517460180992,587950108643300554506240, %U A064074 5249943672359370392053481472,58942155612887708094647422156800,812681867463337890406273965833060352,13499458606943117379769406368204676136960 %N A064074 Generalized tangent number d(9,n). %H A064074 Lars Blomberg, <a href="/A064074/b064074.txt">Table of n, a(n) for n = 1..174</a> %H A064074 D. Shanks, <a href="http://dx.doi.org/10.1090/S0025-5718-1967-0223295-5">Generalized Euler and class numbers</a>. Math. Comp. 21 (1967) 689-694. %H A064074 D. Shanks, <a href="http://dx.doi.org/10.1090/S0025-5718-1968-0227093-9">Corrigenda to: "Generalized Euler and class numbers"</a>, Math. Comp. 22 (1968), 699. %H A064074 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TangentNumber.html">Tangent Number</a>. %F A064074 a(n) = (2*n-1)!*[x^(2*n-1)](sec(9*x)*4*sin(3*x)*cos(3*x)^2). - _Peter Luschny_, Nov 21 2021 %p A064074 egf := sec(9*x)*4*sin(3*x)*cos(3*x)^2: ser := series(egf, x, 24): %p A064074 seq((2*n-1)!*coeff(ser, x, 2*n-1), n = 1..10); # _Peter Luschny_, Nov 21 2021 %Y A064074 Cf. A064070, A349268, A349264. %K A064074 nonn,easy %O A064074 1,1 %A A064074 _Eric W. Weisstein_, Aug 31 2001 %E A064074 Offset changed to 1 by _Lars Blomberg_, Sep 07 2015