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 A146558 #12 Mar 18 2020 04:58:32
%S A146558 1,2,0,16,0,72,0,256,0,0,0,2304,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
%N A146558 Number of order n permutations without collinear triples modulo n.
%H A146558 L. Li, <a href="https://arxiv.org/abs/0802.0572">Collinear triples in permutations</a>, arXiv:0802.0572 [math.CO], 2008.
%F A146558 For prime p>=3, a(p) = 0.
%e A146558 For n=4, there are a(4)=16 permutations without collinear triples: [1, 2, 4, 3], [1, 3, 2, 4], [1, 3, 4, 2], [1, 4, 2, 3], [2, 1, 3, 4], [2, 3, 1, 4], [2, 4, 1, 3], [2, 4, 3, 1], [3, 1, 2, 4], [3, 1, 4, 2], [3, 2, 4, 1], [3, 4, 2, 1], [4, 1, 3, 2], [4, 2, 1, 3], [4, 2, 3, 1], [4, 3, 1, 2]
%o A146558 (PARI) { a(n) = local(p,r,g); r=0; for(j=1,n!, p=numtoperm(n,j); g=1; forvec(v=vector(3,i,[1,n]), if(matdet([1,v[1],p[v[1]];1,v[2],p[v[2]];1,v[3],p[v[3]]])%n==0, g=0; break), 2); if(g,r++)); r }
%Y A146558 Cf. A135538, A146557.
%K A146558 nonn,hard,more
%O A146558 1,2
%A A146558 _Max Alekseyev_, Nov 01 2008
%E A146558 Edited by _Max Alekseyev_, Jun 21 2010
%E A146558 a(14)-a(29) from _Bert Dobbelaere_, Mar 15 2020