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 A255515 #15 Mar 12 2015 12:18:26 %S A255515 1,1,1,2,4,5,9,17,26,46,87,137,246,474,791,1420,2783,4839,8806,17361, %T A255515 31252,57613,114497,211496,395637,791597,1495016,2834242,5710510, %U A255515 10986325,21101677,42796060,83674582,162695172,332141014,658589710,1295551257,2661881254 %N A255515 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 A255515 The fact that A239837(n) is a multiple of n! follows from a general result in group theory due to Solomon. %H A255515 Hiroaki Yamanouchi, <a href="/A255515/b255515.txt">Table of n, a(n) for n = 0..60</a> %H A255515 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 A255515 a(n) = A239837(n)/n!. %Y A255515 Cf. A239837. %K A255515 nonn %O A255515 0,4 %A A255515 _Paul Boddington_, Feb 24 2015 %E A255515 a(14)-a(37) from _Hiroaki Yamanouchi_, Mar 12 2015