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 A009798 #18 Apr 02 2017 12:28:23 %S A009798 1,-6,112,-5488,451840,-57057792,10262228992,-2484525168640, %T A009798 779280513040384,-307370299649556480,148889329569589362688, %U A009798 -86890528715348714192896,60129120979379216762011648 %N A009798 E.g.f. tanh(sin(x)*cos(x)) (odd powers only). %F A009798 a(n):=(-1)^n*sum(k=0..n, 4^(n-k)/(2*k+1)!*sum(i=0..2*k+1, (-1)^i*(2*k+1-2*i)^(2*n+1)*binomial(2*k+1, i))*(sum(j=1..2*k+1, j!*2^(-j)*(-1)^(k+1+j)*stirling2(2*k+1, j)))). - _Vladimir Kruchinin_, Jun 29 2011 %o A009798 (Maxima) %o A009798 a(n):=(-1)^n*sum(4^(n-k)/(2*k+1)!*sum((-1)^i*(2*k+1-2*i)^(2*n+1)*binomial(2*k+1, i), i, 0,2*k+1)*(sum(j!*2^(-j)*(-1)^(k+1+j)*stirling2(2*k+1, j), j, 1, 2*k+1)), k, 0, n); /* _Vladimir Kruchinin_, Jun 28 2011 */ %Y A009798 Cf. A101921. %K A009798 sign %O A009798 0,2 %A A009798 _R. H. Hardin_ %E A009798 Extended with signs by _Olivier Gérard_, Mar 15 1997