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A255515
1/n! times the number of ordered pairs of permutation functions f,g on n elements where f(f(x)) = g(f(g(x))).
1
1, 1, 1, 2, 4, 5, 9, 17, 26, 46, 87, 137, 246, 474, 791, 1420, 2783, 4839, 8806, 17361, 31252, 57613, 114497, 211496, 395637, 791597, 1495016, 2834242, 5710510, 10986325, 21101677, 42796060, 83674582, 162695172, 332141014, 658589710, 1295551257, 2661881254
OFFSET
0,4
COMMENTS
The fact that A239837(n) is a multiple of n! follows from a general result in group theory due to Solomon.
LINKS
Hiroaki Yamanouchi, Table of n, a(n) for n = 0..60
L. Solomon, The solutions of equations in groups, Arch. Math., V.20. no.3, (1969) 241-247.
FORMULA
a(n) = A239837(n)/n!.
CROSSREFS
Cf. A239837.
Sequence in context: A226447 A073151 A279786 * A067298 A077389 A122991
KEYWORD
nonn
AUTHOR
Paul Boddington, Feb 24 2015
EXTENSIONS
a(14)-a(37) from Hiroaki Yamanouchi, Mar 12 2015
STATUS
approved