OFFSET
1,6
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
FORMULA
EXAMPLE
For n = 16, set of such divisors is {1, 8}; a(16) = 2.
MATHEMATICA
Table[DivisorSum[n, 1 &, If[# > 1, #^IntegerExponent[n, #], 1] != n &], {n, 100}] (* Michael De Vlieger, May 27 2017 *)
PROG
(PARI)
A286561(n, k) = if(1==k, 1, valuation(n, k));
(PARI) a(n) = if(n==1, return(0)); my(f=factor(n), g = f[1, 2]); for(i=2, matsize(f)[1], g=gcd(g, f[i, 2])); numdiv(n) - numdiv(g) \\ David A. Corneth, May 27 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Dec 25 2010
STATUS
approved