A239756 Number of pairs of functions (f,g) from a set of n elements into itself satisfying f(f(g(x))) = g(g(x)).

1, 1, 8, 129, 3616, 151845, 8864496, 682005919

Offset

0,3

Links

Table of n, a(n) for n=0..7.

Crossrefs

Cf. A000248, A000949.

Sequence in context: A364986 A338328 A073701 * A295240 A240630 A187609

Adjacent sequences: A239753 A239754 A239755 * A239757 A239758 A239759

Keyword

nonn,more

Author

Chad Brewbaker, Mar 26 2014

Extensions

a(6)-a(7) from Giovanni Resta, Mar 28 2014

Status

approved