A239755 Number of pairs of functions (f,g) from a set of n elements into itself satisfying f(g(x)) = g(f(f(x))).

1, 1, 8, 123, 2776, 86265, 3498336, 179365669

Offset

0,3

Links

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

Crossrefs

Cf. A000248, A000949.

Sequence in context: A349525 A240477 A195247 * A264408 A364985 A376099

Adjacent sequences: A239752 A239753 A239754 * A239756 A239757 A239758

Keyword

nonn,more

Author

Chad Brewbaker, Mar 26 2014

Extensions

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

Status

approved