%I #8 Jan 12 2017 20:12:16
%S 1,3,5,21,108,660,4680,37800,342720,3447360,38102400,459043200,
%T 5987520000,84064780800,1264085222400,20268952704000,345226033152000,
%U 6224529991680000,118443913555968000,2372079457972224000
%N a(n) is the denominator of the coefficient of z^(2n-1) in the Maclaurin expansion of Sqrt[Pi]Erfi[z].
%C Numerators are unity for n>2.
%C Same as A007680/2 for n>2.
%H G. C. Greubel, <a href="/A084253/b084253.txt">Table of n, a(n) for n = 1..445</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Erfi.html">Erfi</a>
%F a(n) = (2*n-1)*(n-1)!/2 for n>2.
%t Join[{1, 3}, Table[(2*n - 1)*n!/(2*n), {n,3,50}]] (* or *) Denominator[ CoefficientList[Series[Sqrt[Pi]*Erf[t], {t, 0, 10}], t]][[2 ;; ;; 2]] (* _G. C. Greubel_, Jan 12 2017 *)
%o (PARI) concat([1,3], for(n=3, 50, print1((2*n-1)*n!/(2*n), ", "))) \\ _G. C. Greubel_, Jan 12 2017
%Y Cf. A007680.
%K nonn,easy
%O 1,2
%A _Eric W. Weisstein_, May 23 2003
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