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 A225846 #15 Sep 08 2022 08:46:05
%S A225846 1,1,1,5,21,4725,1485,14189175,42567525,516891375,11249435925,
%T A225846 714620417135625,2124921731625,16025362854266390625,
%U A225846 605758715891269565625,5703572324950265390625,480509193164339417203125,22913080876041525109331015625,92765509619601316232109375
%N A225846 Denominator of c(n) = 2^(2*n)*(2^(2*n) - 1)/(2*n)!, a coefficient used in the expansion of tan(x) as Sum_{n>=1} c(n)*|Bernoulli(2*n)|*x^(2*n-1).
%D A225846 George Boros and Victor H. Moll, Irresistible integrals, Cambridge University Press (2006), p. 63.
%H A225846 Vincenzo Librandi, <a href="/A225846/b225846.txt">Table of n, a(n) for n = 0..250</a>
%t A225846 Table[2^(2*n)*(2^(2*n)-1)/(2*n)! // Denominator, {n, 0, 20}]
%o A225846 (Magma) [Denominator(2^(2*n)*(2^(2*n)-1)/Factorial(2*n)): n in [0..20]]; // _Vincenzo Librandi_, Jul 17 2013
%Y A225846 Cf. A225845 (numerators), A000367, A002445, A002430, A036279.
%K A225846 nonn,frac,easy
%O A225846 0,4
%A A225846 _Jean-François Alcover_, May 17 2013