OFFSET
1,4
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..16384
EXAMPLE
The positive divisors of 8 are 1, 2, 4, 8. (2-1), (4-1) and (8-1) are relatively prime to 8, so a(8) = 3.
MATHEMATICA
Table[DivisorSum[n, 1 &, CoprimeQ[# - 1, n] &], {n, 105}] (* Michael De Vlieger, Oct 30 2017 *)
PROG
(PARI) A056692(n) = sumdiv(n, d, (1==gcd(d-1, n))); \\ Antti Karttunen, Oct 30 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Aug 10 2000
STATUS
approved