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 A009214 #20 Mar 10 2022 10:22:27
%S A009214 1,2,8,6,-792,-10790,281940,13531350,-260660176,-33714262350,
%T A009214 550333492140,158933551076014,-2777269276818168,-1301993178430302774,
%U A009214 33725324008920743108,17091479764089813623430
%N A009214 E.g.f. exp(x*sin(x)) (even powers only).
%F A009214 a(n)=sum(k=1..n, binomial(2*n,k)*(i=0..k/2, sum((2*i-k)^(2*n-k)*binomial(k,i)*(-1)^(n-i)))/(2^(k-1))). - _Vladimir Kruchinin_, Jun 06 2011
%F A009214 a(0) = 1; a(n) = 2 * Sum_{k=1..n} (-1)^(k+1) * binomial(2*n-1,2*k-1) * k * a(n-k). - _Ilya Gutkovskiy_, Mar 10 2022
%t A009214 nmax = 30; Take[CoefficientList[Series[Exp[x Sin[x]], {x, 0, nmax}], x] Range[0, nmax]!, {1, -1, 2}]
%o A009214 (Maxima)
%o A009214 a(n):=sum(binomial(2*n,k)*(sum((2*i-k)^(2*n-k)*binomial(k,i)*(-1)^(n-i),i,0,k/2))/(2^(k-1)),k,1,n); /* _Vladimir Kruchinin_, Jun 06 2011 */
%o A009214 (PARI) my(x='x+O('x^40), v=Vec(serlaplace(exp(x*sin(x))))); vector(#v\2, k, v[2*k-1]) \\ _Michel Marcus_, Mar 10 2022
%Y A009214 Cf. A009233.
%K A009214 sign
%O A009214 0,2
%A A009214 _R. H. Hardin_
%E A009214 Extended with signs by _Olivier Gérard_, Mar 15 1997