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

Offset: 0

Author

Alois P. Heinz, Sep 22 2017

Keywords

• nonn

Links

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

Crossrefs

Cf. A006882, A051296.

Programs

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);

Formula

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