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 A255440 #21 Mar 21 2023 05:16:42 %S A255440 1,1,4,24,288,3240,74160,1970640,55762560,2271628800,118676275200, %T A255440 5949399456000,389282684313600,31351069535385600,2431871996666112000, %U A255440 227068393053325824000,25547764411931553792000,2795442523571128983552000,350437557048098924371968000 %N A255440 Number of ordered pairs of permutation functions on n elements satisfying f(g(g(g(x)))) = g(g(g(f(x)))). %C A255440 See A239841 for more information and a proof that a(n) is a multiple of n!. %C A255440 a(n) appears be n! * A232218(n). %H A255440 Hiroaki Yamanouchi, <a href="/A255440/b255440.txt">Table of n, a(n) for n = 0..60</a> %Y A255440 Cf. A239841, A232218 %K A255440 nonn %O A255440 0,3 %A A255440 _Paul Boddington_, Feb 24 2015 %E A255440 a(18) from _Hiroaki Yamanouchi_, Mar 13 2015