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%I #7 Oct 07 2018 14:46:14
%S 4051,111396,1830822,23420022,257667120,2564003346,23761098837,
%T 208907298660,1764392910027,14440938630576,115269796672350,
%U 901599089475150,6935143271107130,52608326918749428,394424679767297550,2927811687630339744,21547773469006784856
%N Number of sets of nonempty words with a total of n letters over senary alphabet such that all letters occur at least once in the set.
%H Alois P. Heinz, <a href="/A320207/b320207.txt">Table of n, a(n) for n = 6..1000</a>
%p h:= proc(n, i, k) option remember; `if`(n=0, 1, `if`(i<1, 0,
%p add(h(n-i*j, i-1, k)*binomial(k^i, j), j=0..n/i)))
%p end:
%p a:= n-> (k-> add((-1)^i*binomial(k, i)*h(n$2, k-i), i=0..k))(6):
%p seq(a(n), n=6..25);
%Y Column k=6 of A319501.
%Y Cf. A320216.
%K nonn
%O 6,1
%A _Alois P. Heinz_, Oct 07 2018
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