A355928 Squarefree part of the sum of divisors of n.

1, 3, 1, 7, 6, 3, 2, 15, 13, 2, 3, 7, 14, 6, 6, 31, 2, 39, 5, 42, 2, 1, 6, 15, 31, 42, 10, 14, 30, 2, 2, 7, 3, 6, 3, 91, 38, 15, 14, 10, 42, 6, 11, 21, 78, 2, 3, 31, 57, 93, 2, 2, 6, 30, 2, 30, 5, 10, 15, 42, 62, 6, 26, 127, 21, 1, 17, 14, 6, 1, 2, 195, 74, 114, 31, 35, 6, 42, 5, 186, 1, 14, 21, 14, 3, 33, 30, 5, 10

Offset: 1

Author

Antti Karttunen, Jul 24 2022

Keywords

• nonn

Comments

Not multiplicative.

Links

• Antti Karttunen, Table of n, a(n) for n = 1..20000
• Index entries for sequences related to sigma(n)

Crossrefs

Cf. A000203, A007913, A006532 (positions of 1's), A355929.

Cf. also A080398.

Programs

PARI

A355928(n) = core(sigma(n));

Python

from sympy.ntheory.factor_ import core, divisor_sigma
def A355928(n): return core(divisor_sigma(n)) # Chai Wah Wu, Jul 28 2022

Formula

a(n) = A007913(A000203(n)).

a(n) = A355929(n) + A007913(n).