This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A239749 #19 Jul 21 2014 13:53:01
%S A239749 1,1,6,87,2056,69605,3201696,190933435
%N A239749 Number of ordered pairs of functions f,g on a set of n elements into itself satisfying f(f(x)) = g(f(g(x))).
%e A239749 a(0) = a(1) = 1 since there is only one endofunction for n=0 or 1 and the equation is satisfied trivially. For n=2, each endofunction f on {1,2} is represented by [f(1),f(2)]. The list of a(2) = 6 pairs (f,g) which satisfy the equation is ([1,1], [1,1]), ([1,1], [1,2]), ([1,2], [1,2]), ([1,2], [2,1]), ([2,2], [1,2]), ([2,2], [2,2]). - _Michael Somos_, Mar 26 2014
%Y A239749 Cf. A000248, A000949.
%Y A239749 Related sequences: A053529, A181162, A239749-A239785, A239836-A239841.
%K A239749 nonn,more
%O A239749 0,3
%A A239749 _Chad Brewbaker_, Mar 26 2014
%E A239749 a(6)-a(7) from _Giovanni Resta_, Mar 26 2014