A206714 Number of solutions (n,k) of s(k)=s(n) (mod n), where 1<=k

0, 1, 1, 1, 2, 2, 4, 1, 2, 1, 4, 1, 4, 3, 11, 2, 2, 1, 4, 3, 2, 2, 10, 1, 2, 1, 8, 1, 7, 6, 26, 3, 4, 2, 5, 1, 2, 3, 9, 2, 6, 3, 4, 3, 4, 2, 21, 2, 2, 6, 4, 1, 2, 2, 17, 3, 2, 1, 14, 1, 12, 10, 57, 5, 6, 1, 8, 3, 5, 2, 11, 8, 2, 3, 4, 2, 6, 2, 18, 1, 4, 1, 13, 10, 6, 3, 8, 8, 7, 7, 8, 9, 4

Offset: 2

Author

Clark Kimberling, Feb 11 2012

Keywords

• nonn

Examples

			2^6=64; the numbers 64-s(j) are 63,62,60,56,48,32, of which two are multiples of 6, so that a(6)=2.
		

Programs

Mathematica

s[k_] := 2^(k - 1);
f[n_, k_] := If[Mod[s[n] - s[k], n] == 0, 1, 0];
t[n_] := Flatten[Table[f[n, k], {k, 1, n - 1}]]
a[n_] := Count[Flatten[t[n]], 1]
Table[a[n], {n, 2, 120}] (* A206714 *)