A292778 - OEIS

A292778

INVERT transform of double factorials.

1, 1, 3, 8, 25, 73, 234, 717, 2357, 7480, 25289, 82837, 289518, 980017, 3566993, 12526980, 47916421, 175536777, 712276698, 2736099789, 11863097885, 47932689416, 222692658177, 946323358837, 4700880455462, 20946375415505, 110626016074953, 514550968010964

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OFFSET

0,3

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..807

FORMULA

G.f.: 1 / (1 - Sum_{k>=1} k!! * x^k). - Ilya Gutkovskiy, Dec 14 2019

MAPLE

a:= proc(n) option remember; `if`(n=0, 1,

add(doublefactorial(j)*a(n-j), j=1..n))

end:

seq(a(n), n=0..30);