A323068 Number of divisors d of n such that A049820(d) > 0 and A049820(d) is also a divisor of n.

0, 0, 1, 1, 0, 2, 0, 2, 1, 0, 0, 4, 0, 0, 2, 2, 0, 3, 0, 1, 1, 0, 0, 5, 0, 0, 1, 1, 0, 4, 0, 2, 1, 0, 1, 6, 0, 0, 1, 2, 0, 2, 0, 1, 2, 0, 0, 6, 0, 0, 1, 1, 0, 3, 0, 2, 1, 0, 0, 6, 0, 0, 1, 2, 0, 2, 0, 1, 1, 2, 0, 7, 0, 0, 2, 1, 0, 2, 0, 2, 1, 0, 0, 4, 0, 0, 1, 2, 0, 5, 0, 1, 1, 0, 0, 6, 0, 0, 2, 1, 0, 2, 0, 2, 3

Offset: 1

Author

Antti Karttunen, Jan 05 2019

Keywords

• nonn

Comments

Records 0, 1, 2, 4, 5, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 19, 20, 22, 27, 30, ... occur at n = 1, 3, 6, 12, 24, 36, 72, 144, 240, 360, 720, 1440, 1680, 2640, 3360, 5040, 7920, 10080, 30240, 55440, ...

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10080

Crossrefs

Cf. A000005, A049820, A322358, A323069.

Programs

PARI

A323068(n) = sumdiv(n,d,my(t=(d-numdiv(d))); ((t>0)&&!(n%t)));

Formula

Sum_{d|n} [A049820(d) > 0 and A049820(d)|n], where [ ] is the Iverson bracket.

a(n) >= A323069(n) => A322358(n).