A086669 a(n) = number of divisors of n that are fundamental discriminants.

1, 1, 1, 1, 2, 1, 1, 2, 1, 2, 1, 2, 2, 1, 2, 2, 2, 1, 1, 2, 2, 1, 1, 4, 2, 2, 1, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1, 2, 4, 2, 2, 1, 2, 2, 1, 1, 4, 1, 2, 2, 2, 2, 1, 2, 4, 2, 2, 1, 4, 2, 1, 2, 2, 4, 2, 1, 2, 2, 2, 1, 4, 2, 2, 2, 2, 2, 2, 1, 4, 1, 2, 1, 4, 4, 1, 2, 4, 2, 2, 2, 2, 2, 1, 2, 4, 2, 1, 2, 2

Offset: 1

Author

Jon Perry, Jul 27 2003

Keywords

• nonn

Examples

			10 has divisors 1, 2, 5 and 10 of which 1 and 5 are fundamental discriminants, so a(10)=2
		

Links

• Antti Karttunen, Table of n, a(n) for n = 1..16385

Crossrefs

Cf. A003658, A290098.

Programs

PARI

for (n=1,100,s=0; fordiv(i=n,i,s+=isfundamental(i)); print1(","s))

PARI

A086669(n) = sumdiv(n, i, isfundamental(i)); \\ Antti Karttunen, Aug 22 2017

Formula

a(n) = Sum_{d|n} A290098(d).