A239839 Number of ordered pairs of permutation functions on n elements satisfying f(f(f(x))) = g(f(g(x))).

1, 1, 4, 18, 168, 1560, 20880, 267120, 5080320, 93623040, 2184537600, 49896000000, 1451853849600, 41739720422400, 1426847092070400, 47989033956864000, 1919268439216128000, 76229151152394240000, 3471527082588364800000, 156226856133456396288000

Offset

0,3

Links

Hiroaki Yamanouchi, Table of n, a(n) for n = 0..60

Crossrefs

Cf. A000012, A000085, A000142, A088311, A053529, A001044.

Sequence in context: A222766 A302827 A007153 * A367486 A156870 A240317

Adjacent sequences: A239836 A239837 A239838 * A239840 A239841 A239842

Keyword

nonn

Author

Chad Brewbaker, Mar 27 2014

Extensions

a(8)-a(9) from Giovanni Resta, Mar 27 2014

a(10)-a(13) from Paul Boddington, Feb 23 2015

a(14)-a(19) from Hiroaki Yamanouchi, Mar 12 2015

Status

approved