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 A206589 #5 Mar 30 2012 18:58:12 %S A206589 1,0,2,1,2,1,1,1,1,0,3,1,2,1,2,0,2,0,2,1,2,1,1,0,0,1,1,0,4,1,2,2,2,1, %T A206589 1,1,1,1,3,1,3,1,1,2,1,0,3,1,1,1,1,0,2,1,2,2,1,1,4,0,1,1,0,0,2,0,2,2, %U A206589 3,0,4,1,2,2,1,1,3,1,2,1,2,1,3,1,3,2,3,1,3,0,1,0,2,1,2,0,2,0,2 %N A206589 Number of solutions (n,k) of p(k+1)=p(n+1) (mod n), where 1<=k<n. %C A206589 Related to A206588, which includes differences p-2. %e A206589 For k=1 to 5, the numbers p(7)-p(k+1) are 14,12,10,6,4, so that a(6)=2. %t A206589 f[n_,k_]:=If[Mod[Prime[n+1]-Prime[k+1],n]==0,1,0]; %t A206589 t[n_] := Flatten[Table[f[n, k], {k, 1, n - 1}]] %t A206589 a[n_] := Count[Flatten[t[n]], 1] %t A206589 Table[a[n], {n, 2, 120}] (* A206589 *) %Y A206589 Cf. A206588. %K A206589 nonn %O A206589 2,3 %A A206589 _Clark Kimberling_, Feb 09 2012