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

1,6

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

Formula

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

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

Prog

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

Crossrefs

Cf. A000005, A049820, A322358, A323069.

Sequence in context: A262774 A112604 A203399 * A072627 A277144 A069848

Adjacent sequences: A323065 A323066 A323067 * A323069 A323070 A323071

Keyword

nonn

Author

Antti Karttunen, Jan 05 2019

Status

approved