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 A136606 #12 Feb 16 2025 08:33:07
%S A136606 1,6,24,5040,72576,39916800,95800320,1307674368000,4184557977600,
%T A136606 121645100408832000,2043637686868377600,25852016738884976640000,
%U A136606 238634000666630553600000,10888869450418352160768000000
%N A136606 Reduced denominators in the Maclaurin series for the Gudermannian.
%D A136606 Jerome Spanier and Keith B. Oldham, "Atlas of Functions", Hemisphere Publishing Corp., 1987, chapter 33, equation 33:14:14 at page 318.
%H A136606 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Gudermannian.html">Gudermannian</a>.
%H A136606 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/InverseGudermannian.html">Inverse Gudermannian</a>.
%e A136606 x - x^3/6 + x^5/24 - (61*x^7)/5040 + (277*x^9)/72576 - ...
%t A136606 gd[x_] := 2*ArcTan[(E^x - 1)/(E^x + 1)]; CoefficientList[ Series[gd[x], {x, 0, 28}]/x , x^2] // Denominator (* _Jean-François Alcover_, Nov 09 2012 *)
%Y A136606 Cf. A091912.
%K A136606 nonn
%O A136606 1,2
%A A136606 _Eric W. Weisstein_, Jan 12 2008