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 A009515 #19 Sep 24 2019 12:16:21 %S A009515 0,2,8,-24,-4544,-333920,-26272896,-2354853760,-233143441408, %T A009515 -22905309777408,-1339233237800960,428177363623094272, %U A009515 310125853369485017088,153488683972244927062016,72759436391841580585680896 %N A009515 E.g.f. sin(x*tan(x)) (even powers only). %F A009515 a(n)=(sum(m=0..n-1/2, binomial(2*n,2*m+1)*(sum(j=2*m+1..2*n-2*m-1, binomial(j-1,2*m)*j!*(-1)^(n+m+j)*2^(2*n-2*m-j-1)*stirling2(2*n-2*m-1,j))))). - _Vladimir Kruchinin_, Jun 23 2011 %t A009515 terms = 15; %t A009515 egf = Sin[x*Tan[x]] + O[x]^(2 terms + 1) ; %t A009515 Partition[CoefficientList[egf, x] * Range[0, 2 terms]!, 2][[All, 1]] (* _Jean-François Alcover_, Sep 24 2019 *) %o A009515 (Maxima) %o A009515 a(n):=(sum(binomial(2*n,2*m+1)*(sum(binomial(j-1,2*m)*j!*(-1)^(n+m+j)*2^(2*n-2*m-j-1)*stirling2(2*n-2*m-1,j),j,2*m+1,2*n-2*m-1)),m,0,n-1/2)); /* _Vladimir Kruchinin_, Jun 23 2011 */ %K A009515 sign %O A009515 0,2 %A A009515 _R. H. Hardin_ %E A009515 Extended with signs by _Olivier Gérard_, Mar 15 1997