A336691 Number of distinct prime factors of 1+sigma(n).

1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 2, 2, 1, 2, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 2, 2, 1, 2, 2, 1, 1, 2, 2, 1, 1, 1, 1, 2, 2, 1, 2, 2, 1, 1, 1, 1, 2, 1, 1, 2, 1, 3, 1, 2, 2, 2, 1, 1, 2, 1, 2, 2, 2, 1, 2, 1, 1, 1, 2, 2, 1, 2, 2, 1, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 2, 2, 2, 1, 2, 1, 2, 3, 1, 1

Offset: 1

Author

Antti Karttunen, Jul 31 2020

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..65537
• Index entries for sequences related to sigma(n)

Crossrefs

Cf. A000203, A001221, A088580, A058062, A332459, A336692, A336693, A336694, A336695.

Programs

PARI

A336691(n) = omega(1+sigma(n));

Formula

a(n) = A001221(1+A000203(n)) = A001221(A088580(n)).