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%I #14 Jan 01 2019 07:01:07
%S 1,1,1,2,3,12,25,150,378,1960,8154,81540,261250,3135000,19358040,
%T 160331626,719579700,11513275200,62702704800,1128648686400,
%U 7122671957664,88475482100520,905279068633800,19916139509943600
%N Number of permutations of {1,2,...,n} in which each element follows its proper divisors.
%H Sean A. Irvine, <a href="/A016021/b016021.txt">Table of n, a(n) for n = 0..45</a>
%e 12 valid permutations for a(5): 12345 12354 12435 12453 12534 12543 13245 13254 13524 15234 15243 15324.
%K nonn
%O 0,4
%A _David W. Wilson_, Jun 07 2000