A245503 Number of endofunctions f on [n] such that f^7(i) = f(i) for all i in [n].

1, 1, 4, 21, 142, 1131, 10422, 112015, 1396516, 19702665, 306547426, 5177584809, 94168757916, 1833590759131, 38009888806450, 835064706091431, 19389119390412448, 475039405292487825, 12263445905182200882, 332913448508180564521, 9478703390668813103836

Offset

0,3

Links

Alois P. Heinz, Table of n, a(n) for n = 0..200

Formula

E.g.f.: exp(x*exp(x)+x^2*exp(x)^2/2+x^3*exp(x)^3/3+x^6*exp(x)^6/6).

Maple

egf:= exp(x*exp(x)+x^2*exp(x)^2/2+x^3*exp(x)^3/3+x^6*exp(x)^6/6):
a:= n-> n!*coeff(series(egf, x, n+1), x, n):
seq(a(n), n=0..25);

Crossrefs

Column k=7 of A245501.

Sequence in context: A222058 A265174 A087761 * A120368 A053482 A158577

Adjacent sequences: A245500 A245501 A245502 * A245504 A245505 A245506

Keyword

nonn

Author

Alois P. Heinz, Jul 24 2014

Status

approved