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1/n! times the number of ordered pairs of permutation functions f,g on n elements where f(f(x)) = g(f(g(x))).
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%I #15 Mar 12 2015 12:18:26

%S 1,1,1,2,4,5,9,17,26,46,87,137,246,474,791,1420,2783,4839,8806,17361,

%T 31252,57613,114497,211496,395637,791597,1495016,2834242,5710510,

%U 10986325,21101677,42796060,83674582,162695172,332141014,658589710,1295551257,2661881254

%N 1/n! times the number of ordered pairs of permutation functions f,g on n elements where f(f(x)) = g(f(g(x))).

%C The fact that A239837(n) is a multiple of n! follows from a general result in group theory due to Solomon.

%H Hiroaki Yamanouchi, <a href="/A255515/b255515.txt">Table of n, a(n) for n = 0..60</a>

%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) = A239837(n)/n!.

%Y Cf. A239837.

%K nonn

%O 0,4

%A _Paul Boddington_, Feb 24 2015

%E a(14)-a(37) from _Hiroaki Yamanouchi_, Mar 12 2015