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%I #8 Dec 14 2019 19:23:45
%S 1,1,3,8,25,73,234,717,2357,7480,25289,82837,289518,980017,3566993,
%T 12526980,47916421,175536777,712276698,2736099789,11863097885,
%U 47932689416,222692658177,946323358837,4700880455462,20946375415505,110626016074953,514550968010964
%N INVERT transform of double factorials.
%H Alois P. Heinz, <a href="/A292778/b292778.txt">Table of n, a(n) for n = 0..807</a>
%F G.f.: 1 / (1 - Sum_{k>=1} k!! * x^k). - _Ilya Gutkovskiy_, Dec 14 2019
%p a:= proc(n) option remember; `if`(n=0, 1,
%p add(doublefactorial(j)*a(n-j), j=1..n))
%p end:
%p seq(a(n), n=0..30);
%Y Cf. A006882, A051296.
%K nonn
%O 0,3
%A _Alois P. Heinz_, Sep 22 2017
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