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A255525
1/n! times the number of ordered pairs of permutation functions f,g on n elements where f(g(g(x))) = g(f(f(x))).
0
1, 1, 1, 1, 2, 3, 4, 6, 9, 13, 17, 27, 31, 42, 57, 83, 104
OFFSET
0,5
COMMENTS
The fact that A239836(n) is a multiple of n! follows from a general result in group theory due to Solomon.
LINKS
L. Solomon, The solutions of equations in groups, Arch. Math., V.20. no.3, (1969) 241-247.
FORMULA
a(n) = A239836(n)/n!.
CROSSREFS
Cf. A239836.
Sequence in context: A123648 A244393 A286929 * A129632 A016028 A239551
KEYWORD
nonn,more
AUTHOR
Paul Boddington, Feb 24 2015
STATUS
approved