A389089 Denominator of ratio sigma(n) / A048250(n), where sigma is the sum of divisors and A048250 is the sum of squarefree divisors.

1, 1, 1, 3, 1, 1, 1, 1, 4, 1, 1, 3, 1, 1, 1, 3, 1, 4, 1, 3, 1, 1, 1, 1, 6, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 12, 1, 1, 1, 1, 1, 1, 1, 3, 4, 1, 1, 3, 8, 6, 1, 3, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 4, 3, 1, 1, 1, 3, 1, 1, 1, 4, 1, 1, 6, 3, 1, 1, 1, 3, 4, 1, 1, 3, 1, 1, 1, 1, 1, 4, 1, 3, 1, 1, 1, 1, 1, 8, 4, 18, 1, 1, 1, 1, 1

Offset

1,4

Comments

First differs from A367990 at n = 196.

As an integer this sequence by itself is not multiplicative, as for example a(4) = 3, a(49) = 8, but a(196) = 8 <> 3*8. See also comment in A389087.

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries for sequences related to sigma(n).

Formula

a(n) = A048250(n) / A389080(n).

Prog

(PARI)
A048250(n) = factorback(apply(p -> p+1, factor(n)[, 1]));
A389089(n) = denominator(sigma(n)/A048250(n));

Crossrefs

Cf. A000203, A048250, A389080, A389087 (numerators).

Cf. also A367990, A389075.

Sequence in context: A016465 A122947 A367990 * A360162 A367988 A372692

Adjacent sequences: A389086 A389087 A389088 * A389090 A389091 A389092

Keyword

nonn,frac

Author

Antti Karttunen, Oct 03 2025

Status

approved