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Smallest k such that k*n is a double factorial.
1

%I #19 Feb 19 2018 09:32:28

%S 1,1,1,2,3,8,15,1,105,384,945,4,10395,46080,1,3,2027025,2560,34459425,

%T 192,5,3715891200,13749310575,2,81081,1961990553600,35,23040,

%U 213458046676875,128,6190283353629375,12

%N Smallest k such that k*n is a double factorial.

%H Robert G. Wilson v, <a href="/A007919/b007919.txt">Table of n, a(n) for n = 1..817</a>

%H F. Smarandache, <a href="http://www.gallup.unm.edu/~smarandache/OPNS.pdf">Only Problems, Not Solutions!</a>.

%H <a href="/index/Fa#factorial">Index entries for sequences related to factorial numbers</a>

%t f[n_] := Block[{k = 1}, While[Mod[k!!, n] > 0, k++]; k!!/n]; Array[f, 35] (* _Robert G. Wilson v_, Feb 18 2018 *)

%Y Cf. A006882.

%K nonn

%O 1,4

%A R. Muller

%E a(10) corrected by _Sean A. Irvine_, Feb 18 2018