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A245986 Number of pairs of endofunctions f, g on [n] satisfying g^9(f(i)) = f(i) for all i in [n]. 2
1, 1, 6, 141, 6184, 387545, 33404256, 3891981205, 592320594048, 128805405787953, 43012267760166400, 19329826195760619341, 10086545470056599549952, 5787171311384573282516617, 3623228151360430287454531584, 2480483584581055916081566933125 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..100

MAPLE

with(combinat): M:=multinomial:

b:= proc(n, k) local l, g; l, g:= [1, 3, 9],

      proc(k, m, i, t) option remember; local d, j; d:= l[i];

        `if`(i=1, n^m, add(M(k, k-(d-t)*j, (d-t)$j)/j!*

         (d-1)!^j *M(m, m-t*j, t$j) *g(k-(d-t)*j, m-t*j,

        `if`(d-t=1, [i-1, 0], [i, t+1])[]), j=0..min(k/(d-t),

        `if`(t=0, [][], m/t))))

      end; g(k, n-k, nops(l), 0)

    end:

a:= n-> add(b(n, j)*stirling2(n, j)*binomial(n, j)*j!, j=0..n):

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

CROSSREFS

Column k=9 of A245980.

Sequence in context: A193502 A059488 A241015 * A225810 A067196 A286446

Adjacent sequences:  A245983 A245984 A245985 * A245987 A245988 A245989

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Aug 08 2014

STATUS

approved

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Last modified March 28 11:00 EDT 2020. Contains 333083 sequences. (Running on oeis4.)