A084253 a(n) is the denominator of the coefficient of z^(2n-1) in the Maclaurin expansion of Sqrt[Pi]Erfi[z].

1, 3, 5, 21, 108, 660, 4680, 37800, 342720, 3447360, 38102400, 459043200, 5987520000, 84064780800, 1264085222400, 20268952704000, 345226033152000, 6224529991680000, 118443913555968000, 2372079457972224000

Offset: 1

Author

Eric W. Weisstein, May 23 2003

Keywords

• nonn
• easy

Comments

Numerators are unity for n>2.

Same as A007680/2 for n>2.

Links

• G. C. Greubel, Table of n, a(n) for n = 1..445
• Eric Weisstein's World of Mathematics, Erfi

Crossrefs

Cf. A007680.

Programs

Mathematica

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 *)

PARI

concat([1,3], for(n=3, 50, print1((2*n-1)*n!/(2*n), ", "))) \\ G. C. Greubel, Jan 12 2017

Formula

a(n) = (2*n-1)*(n-1)!/2 for n>2.