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A086669 a(n) = number of divisors of n that are fundamental discriminants. 3
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 (list; graph; refs; listen; history; text; internal format)
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: A253051 A103684 A105103 * A053574 A321944 A065203

Adjacent sequences:  A086666 A086667 A086668 * A086670 A086671 A086672

KEYWORD

nonn

AUTHOR

Jon Perry, Jul 27 2003

STATUS

approved

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Last modified April 18 12:42 EDT 2019. Contains 322209 sequences. (Running on oeis4.)