A239757 Number of pairs of functions (f,g) from a set of n elements into itself satisfying f(g(g(x))) = g(f(f(x))).

1, 1, 8, 141, 4192, 178225, 10218096, 762401773

Offset

0,3

Links

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

Crossrefs

Cf. A000248, A000949.

Sequence in context: A090931 A367199 A376094 * A295242 A305763 A180357

Adjacent sequences: A239754 A239755 A239756 * A239758 A239759 A239760

Keyword

nonn,more

Author

Chad Brewbaker, Mar 26 2014

Extensions

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

Status

approved