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 A239753 #12 Dec 25 2023 17:40:02 %S A239753 1,1,8,87,1312,24685,564336,15168811 %N A239753 Number of pairs of functions (f,g) on a set of n elements into itself satisfying f(x) = g(f(g(x))). %F A239753 a(n) <= n^2n. - _Charles R Greathouse IV_, Mar 26 2014 %Y A239753 Cf. A000248, A000949. %K A239753 nonn,more %O A239753 0,3 %A A239753 _Chad Brewbaker_, Mar 26 2014 %E A239753 a(6)-a(7) from _Giovanni Resta_, Mar 28 2014