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 A226180 #7 Jul 17 2013 07:17:37
%S A226180 1,9,75,2205,25515,1715175,79053975,9577693125,184530220875,
%T A226180 35266981624875,4092826025413125,66711917764366875,
%U A226180 92454016466921484375,35047468562280596296875,7641646200968365570359375,3798425171964103092990703125,133435000395771234460221796875
%N A226180 Denominators in Taylor series for integral of tan(x)/x.
%C A226180 Numerators are the same as those from the expansion of tan(x).
%C A226180 Unlike the "sine integral" function Si(x), it seems that there does not exist a "tan integral" function.
%H A226180 Vincenzo Librandi, <a href="/A226180/b226180.txt">Table of n, a(n) for n = 1..100</a>
%F A226180 A036279(n)*(2n-1).
%t A226180 a[n_] := Denominator[(-1)^(n-1)*4^n*(4^n-1)*BernoulliB[2*n]/(2*n)!]*(2*n-1); Table[a[n], {n, 1, 17}]
%Y A226180 Cf. A002430 (Numerators for tan(x)), A036279 (Denominators for tan(x)), A000367, A002445.
%K A226180 nonn,frac
%O A226180 1,2
%A A226180 _Jean-François Alcover_, May 30 2013