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A245983 Number of pairs of endofunctions f, g on [n] satisfying g^6(f(i)) = f(i) for all i in [n]. 2
1, 1, 10, 267, 12040, 826245, 86252976, 12661148311, 2428606888576, 585229569018921, 172640322717932800, 60933514918456147011, 25283156000087876668416, 12189356237264450125373869, 6769905753950075837079906304, 4297777320612236566890778059375 (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, 2, 3, 6],

      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=6 of A245980.

Sequence in context: A060608 A003388 A055408 * A166811 A089906 A294515

Adjacent sequences:  A245980 A245981 A245982 * A245984 A245985 A245986

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Aug 08 2014

STATUS

approved

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Last modified February 17 17:27 EST 2019. Contains 320222 sequences. (Running on oeis4.)