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 A289488 #31 Mar 01 2023 11:50:32
%S A289488 1,3,5,105,945,3465,135135,2027025,883575,654729075,13749310575,
%T A289488 8108567775,718713961875,213458046676875,121378104973125,
%U A289488 191898783962510625,372509404162520625,73881031825566590625,8200794532637891559375,319830986772877770815625
%N A289488 a(n) = denominator of Sum_{k=1..n} 1/(2*k-1)!!.
%H A289488 Seiichi Manyama, <a href="/A289488/b289488.txt">Table of n, a(n) for n = 1..404</a>
%H A289488 OEIS Wiki, <a href="/wiki/A_remarkable_formula_of_Ramanujan">A remarkable formula of Ramanujan</a>
%F A289488 Denominators of coefficients in expansion of sqrt(Pi*x*exp(x)/2) * erf(sqrt(x/2)) / (1 - x). - _Ilya Gutkovskiy_, May 24 2022
%e A289488 1, 4/3, 7/5, 148/105, 1333/945, 4888/3465, 190633/135135, 2859496/2027025, 1246447/883575, 923617228/654729075, 19395961789/13749310575, 11438644132/8108567775, ... = A289381(n)/a(n) -> A060196.
%t A289488 Accumulate[Table[1/(2k-1)!!,{k,20}]]//Denominator (* _Harvey P. Dale_, Mar 01 2023 *)
%Y A289488 Cf. A001147, A060196, A289381, A354299.
%K A289488 nonn,frac
%O A289488 1,2
%A A289488 _Seiichi Manyama_, Sep 02 2017