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 A165960 #12 Apr 14 2021 07:32:37 %S A165960 1,1,2,3,20,100,612,4389,35688,325395,3288490,36489992,441093864, %T A165960 5770007009,81213878830,1223895060315,19662509071056,335472890422812, %U A165960 6057979285535388,115434096553014565,2314691409652237700,48723117262650147387,1074208020519710570054 %N A165960 Number of permutations of length n without modular 3-sequences. %C A165960 Modular 3-sequences are of the following form: i,i+1,i+2, where arithmetic is modulo n. %H A165960 Alois P. Heinz, <a href="/A165960/b165960.txt">Table of n, a(n) for n = 0..450</a> %F A165960 a(n) = n * A165961(n). %e A165960 For n=3 the a(3) = 3 solutions are (0,2,1), (1,0,2) and (2,1,0). %Y A165960 Cf. A002628, A165961, A165962. %K A165960 nonn %O A165960 0,3 %A A165960 _Isaac Lambert_, Oct 01 2009 %E A165960 a(0)-a(2) and a(15)-a(22) from _Alois P. Heinz_, Apr 14 2021