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 A221094 #8 Aug 03 2020 15:37:42
%S A221094 1,1,3,21,263,5165,146335,5649397,285069735,18214525629,1437313035887,
%T A221094 137272113393413,15605422414146487,2082375903282194893,
%U A221094 322303158660868063359,57271523430269553109269,11579903781095519639058119,2643368434346324374530280157,676521525314300179793917303951
%N A221094 O.g.f.: Sum_{n>=0} n!^2 * x^n / Product_{k=1..n} (1 + k*(n-k+1)*x).
%C A221094 Compare to: Sum_{n>=0} n!^2 * x^n / Product_{k=1..n} (1 + k^2*x) = Sum_{n>=0} A110501(n)*x^n, where A110501 is unsigned Genocchi numbers of even index.
%e A221094 G.f.: A(x) = 1 + x + 3*x^2 + 21*x^3 + 263*x^4 + 5165*x^5 + 146335*x^6 +...
%e A221094 where
%e A221094 A(x) = 1 + x/(1+x) + 2!^2*x^2/((1+1*2*x)*(1+2*1*x)) + 3!^2*x^3/((1+1*3*x)*(1+2*2*x)*(1+3*1*x)) + 4!^2*x^4/((1+1*4*x)*(1+2*3*x)*(1+3*2*x)*(1+4*1*x)) + 5!^2*x^5/((1+1*5*x)*(1+2*4*x)*(1+3*3*x)*(1+4*2*x)*(1+5*1*x)) +...
%t A221094 CoefficientList[Series[Sum[(n!)^2 x^n/Product[1+k(n-k+1)x,{k,n}],{n,0,20}],{x,0,20}],x] (* _Harvey P. Dale_, Aug 03 2020 *)
%o A221094 (PARI) {a(n)=polcoeff(sum(m=0, n, m!^2*x^m/prod(k=1, m, 1+(m-k+1)*k*x+x*O(x^n))), n)}
%o A221094 for(n=0, 20, print1(a(n), ", "))
%K A221094 nonn
%O A221094 0,3
%A A221094 _Paul D. Hanna_, Jan 03 2013