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 A239837 #16 Mar 12 2015 12:17:58 %S A239837 1,1,2,12,96,600,6480,85680,1048320,16692480,315705600,5468601600, %T A239837 117834393600,2951607859200,68958028339200,1856897602560000, %U A239837 58228124258304000,1721171464556544000,56379302852640768000,2111880588197732352000,76033053559536353280000 %N A239837 Number of ordered pairs of permutation functions on n elements satisfying f(f(x)) = g(f(g(x))). %H A239837 Hiroaki Yamanouchi, <a href="/A239837/b239837.txt">Table of n, a(n) for n = 0..60</a> %Y A239837 Cf. A000012, A000085, A000142, A088311, A053529, A001044. %K A239837 nonn %O A239837 0,3 %A A239837 _Chad Brewbaker_, Mar 27 2014 %E A239837 a(8)-a(9) from _Giovanni Resta_, Mar 27 2014 %E A239837 a(10)-a(13) from _Paul Boddington_, Feb 23 2015 %E A239837 a(14)-a(20) from _Hiroaki Yamanouchi_, Mar 12 2015