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A239839
Number of ordered pairs of permutation functions on n elements satisfying f(f(f(x))) = g(f(g(x))).
2
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
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