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A084253
a(n) is the denominator of the coefficient of z^(2n-1) in the Maclaurin expansion of Sqrt[Pi]Erfi[z].
1
1, 3, 5, 21, 108, 660, 4680, 37800, 342720, 3447360, 38102400, 459043200, 5987520000, 84064780800, 1264085222400, 20268952704000, 345226033152000, 6224529991680000, 118443913555968000, 2372079457972224000
OFFSET
1,2
COMMENTS
Numerators are unity for n>2.
Same as A007680/2 for n>2.
LINKS
Eric Weisstein's World of Mathematics, Erfi
FORMULA
a(n) = (2*n-1)*(n-1)!/2 for n>2.
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 *)
PROG
(PARI) concat([1, 3], for(n=3, 50, print1((2*n-1)*n!/(2*n), ", "))) \\ G. C. Greubel, Jan 12 2017
CROSSREFS
Cf. A007680.
Sequence in context: A216385 A247680 A179265 * A153889 A364576 A186751
KEYWORD
nonn,easy
AUTHOR
Eric W. Weisstein, May 23 2003
STATUS
approved