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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))).
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%I #9 Feb 27 2015 10:51:09

%S 1,1,1,1,2,3,4,6,9,13,17,27,31,42,57,83,104

%N 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))).

%C The fact that A239836(n) is a multiple of n! follows from a general result in group theory due to Solomon.

%H L. Solomon, <a href="http://dx.doi.org/10.1007/BF01899292">The solutions of equations in groups</a>, Arch. Math., V.20. no.3, (1969) 241-247.

%F a(n) = A239836(n)/n!.

%Y Cf. A239836.

%K nonn,more

%O 0,5

%A _Paul Boddington_, Feb 24 2015