%I #16 Nov 03 2019 19:40:10
%S 1,3,45,1890,56700,748440,10216206000,8756748000,2841962760000,
%T 24946749107280000,8232427205402400000,103279541304139200000,
%U 3101484625363300176000000,1431454442475369312000000
%N Denominators of the coefficients of the polynomials 1/Sum_{n>=1} x^(n-1)/((2*n)!/n!) = 2*exp(-x/4)*sqrt(x)/ (sqrt(Pi)*erf(sqrt(x)/2)).
%H G. C. Greubel, <a href="/A154242/b154242.txt">Table of n, a(n) for n = 0..250</a>
%F a(n) = denominator([x^n]*(1/Sum_{k>=1} x^(k-1)/((2*k)!/k!)).
%F a(n) = denominator([x^n]*2*exp(-x/4)*sqrt(x)/(sqrt(Pi)*erf(sqrt(x)/2)))).
%t p[x] := FullSimplify[1/Sum[x^(n - 1)/((2*n)!/n!), {n, 1, Infinity}]];
%t Table[ Denominator[SeriesCoefficient[Series[p[x], {x, 0, 30}], n]], {n, 0, 30}]
%t Table[Denominator[SeriesCoefficient[Series[2*Exp[-x/4]*Sqrt[x]/(Sqrt[Pi]*Erf[Sqrt[x]/2]), {x, 0, 30}], n]], {n, 0, 50}] (* _G. C. Greubel_, Sep 07 2016 *)
%o (PARI) seq(n)={[denominator(t) | t<-Vec(1/sum(k=1, n, x^(k-1)/((2*k)!/k!), O(x^n)))]} \\ _Andrew Howroyd_, Nov 02 2019
%K nonn,frac
%O 0,2
%A _Roger L. Bagula_, Jan 05 2009