OFFSET
1,2
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
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
KEYWORD
nonn,easy
AUTHOR
Eric W. Weisstein, May 23 2003
STATUS
approved