OFFSET
1,2
EXAMPLE
5 divides exactly two of the numbers s(n)-s(k) for k=1,2,3,4, so that a(5)=2.
MATHEMATICA
s[k_] := k (k + 1) (k + 2)/6;
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}] (* A206826 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Clark Kimberling, Feb 12 2012
STATUS
approved