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 A117988 #16 Jul 23 2024 10:25:05
%S A117988 1,4,6,16,18,576,78,1728,1365,5184,486,2985984,3474,389376,13583700,
%T A117988 268435456,65538,119246400,45006,39261044736,21400013700,15116544,
%U A117988 67590,45476068117708800,8696104065,772395264,19496328075,1822309056774144,231340050
%N A117988 Number of functions f:[n]->[n] such that f[(x^2) mod n]=[f(x)^2] mod n for all x in [n], for n=1,2,3,... Here [n] denotes {0,1,2,...,n-1}.
%C A117988 See A117986 and A117987 for results on other modular functional equations.
%H A117988 Rémy Sigrist, <a href="/A117988/b117988.txt">Table of n, a(n) for n = 1..767</a>
%H A117988 Rémy Sigrist, <a href="/A117988/a117988.gp.txt">PARI program for A117988</a>
%o A117988 (PARI) \\ See Links section.
%Y A117988 Cf. A023153, A117986, A117987.
%K A117988 nonn
%O A117988 1,2
%A A117988 _John W. Layman_, Apr 14 2006
%E A117988 More terms from _Rémy Sigrist_, Sep 20 2019