A245915 - OEIS

%I #4 Aug 06 2014 15:08:37

%S 1,1,12,297,11104,578745,46097856,4892935369,649893820416,

%T 108501530261841,21500188932505600,4911081373878751401,

%U 1343217062946070130688,427404076347462876047113,154711214699181287350984704,64222714159878924347124911625

%N Number of pairs of endofunctions f, g on [n] satisfying f(g^6(i)) = f(i) for all i in [n].

%H Alois P. Heinz, <a href="/A245915/b245915.txt">Table of n, a(n) for n = 0..150</a>

%p with(combinat):

%p b:= proc(n, i) option remember; unapply(`if`(n=0 or i=1, x^n,

%p       expand(add((i-1)!^j*multinomial(n, n-i*j, i$j)/j!*

%p       x^(igcd(i, 6)*j)*b(n-i*j, i-1)(x), j=0..n/i))), x)

%p     end:

%p a:= n-> add(binomial(n-1, j-1)*n^(n-j)*b(j$2)(n), j=0..n):

%p seq(a(n), n=0..20);

%Y Column k=6 of A245910.

%K nonn

%O 0,3

%A _Alois P. Heinz_, Aug 06 2014