cp's OEIS Frontend

A108499 Number of values of k (1<=k<=n) where k^(n+1) = k mod n, or equivalently where sum_i{1<=i<=n} k^i = 0 mod n.

%I A108499 #25 Nov 17 2020 14:47:39
%S A108499 1,2,2,3,2,6,2,5,4,6,2,9,2,6,4,9,2,14,2,15,8,6,2,15,6,6,10,9,2,18,2,
%T A108499 17,4,6,4,21,2,6,8,25,2,42,2,9,8,6,2,27,8,22,4,15,2,38,12,15,8,6,2,45,
%U A108499 2,6,16,33,4,18,2,15,4,18,2,35,2,6,12,9,4,42,2,45,28,6,2,63,4,6,4,15,2,42,4
%N A108499 Number of values of k (1<=k<=n) where k^(n+1) = k mod n, or equivalently where sum_i{1<=i<=n} k^i = 0 mod n.
%F A108499 a(n)=n-A108500(n). a(n)=n iff n is in A014117.
%e A108499 a(2)=2 since 1^3 = 1 mod 2 and 2^3 = 8 = 0 mod 2 = 2 mod 2.
%e A108499 a(3)=2 since 1^1+1^2+1^3 = 3 = 0 mod 3 and 3^1+3^2+3^3 = 39 = 0 mod 3 but 2^1+2^2+2^3 = 14 = 2 mod 3 != 0 mod 3.
%Y A108499 Numbers of zeros in rows of A108497 or A108498.
%K A108499 nonn
%O A108499 1,2
%A A108499 _Henry Bottomley_, Jun 06 2005