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 A334066 #18 Apr 30 2020 02:23:16
%S A334066 1,5,34,298,3207,40947,605076,10157220,190915965,3971997585,
%T A334066 90613969110,2249113016430,60338869272675,1739831420490975,
%U A334066 53656981894391400,1762410972384203400,61421841416041392825,2263752327235180060125,87970054921758957890250
%N A334066 a(n) = (2n-1)!!*(Sum_{k=1..n}k/(2*k-1)).
%F A334066 a(n) = (2n-1)!!*(Sum_{k=1..n}k/(2*k-1)).
%F A334066 Recurrence: a(n) = 2*a(n-1) + (2*n-3)^2*a(n-2) + (2*n-1)!!.
%e A334066 a(4)=298 since 1/1+2/3+3/5+4/7=298/105=298/(7!!).
%t A334066 Table[Sum[k/(2*k-1), {k, 1, n}], {n, 1, 19}]*Table[Product[2*j-1, {j, 1, n}], {n, 1, 19}]
%t A334066 FullSimplify[Table[(n/2 + HarmonicNumber[n - 1/2]/4 + Log[2]/2) * (2*n-1)!!, {n, 1, 20}]] (* _Vaclav Kotesovec_, Apr 14 2020 *)
%Y A334066 Cf. A004041.
%K A334066 nonn,easy
%O A334066 1,2
%A A334066 _Greg Huber_, Apr 13 2020