login
A389089
Denominator of ratio sigma(n) / A048250(n), where sigma is the sum of divisors and A048250 is the sum of squarefree divisors.
5
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.
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
KEYWORD
nonn,frac
AUTHOR
Antti Karttunen, Oct 03 2025
STATUS
approved