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 A368792 #11 Sep 04 2025 14:10:24
%S A368792 0,1,5,28,200,1805,19861,258200,3873008,65841145,1250981765,
%T A368792 26270617076,604224192760,15105604819013,407851330113365,
%U A368792 11827688573287600,366658345771915616,12099725410473215345,423490389366562537093,15669144406562813872460
%N A368792 a(n) = (2*n-1)!! * Sum_{k=0..n} k/(2*k-1)!!.
%F A368792 a(0) = 0; a(n) = (2*n-1)*a(n-1) + n.
%t A368792 Table[(2n-1)!!Sum[k/(2k-1)!!,{k,0,n}],{n,0,20}] (* _Harvey P. Dale_, Sep 04 2025 *)
%o A368792 (PARI) a001147(n) = prod(k=1, n, 2*k-1);
%o A368792 a(n) = a001147(n)*sum(k=0, n, k/a001147(k));
%Y A368792 Cf. A001147, A286286, A368793.
%K A368792 nonn,easy,changed
%O A368792 0,3
%A A368792 _Seiichi Manyama_, Jan 05 2024