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

1,5

Links

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

Formula

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

Example

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

Prog

(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

Crossrefs

Cf. A003658, A290098.

Sequence in context: A105103 A377648 A376365 * A357906 A053574 A321944

Adjacent sequences: A086666 A086667 A086668 * A086670 A086671 A086672

Keyword

nonn

Author

Jon Perry, Jul 27 2003

Status

approved