A344774 Number of divisors d of n for which A049559(d) = A049559(n), where A049559(n) = gcd(n-1, phi(n)).

1, 2, 1, 3, 1, 3, 1, 4, 2, 3, 1, 5, 1, 3, 2, 5, 1, 4, 1, 5, 1, 3, 1, 7, 2, 3, 3, 1, 1, 5, 1, 6, 1, 3, 1, 7, 1, 3, 2, 7, 1, 5, 1, 5, 2, 3, 1, 9, 2, 4, 2, 1, 1, 5, 1, 6, 1, 3, 1, 9, 1, 3, 3, 7, 1, 1, 1, 5, 1, 1, 1, 10, 1, 3, 3, 1, 1, 5, 1, 9, 4, 3, 1, 8, 2, 3, 2, 7, 1, 7, 1, 5, 1, 3, 1, 11, 1, 4, 3, 7, 1, 5, 1, 6, 1

Offset: 1

Author

Antti Karttunen, May 31 2021

Keywords

• nonn

Links

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

Crossrefs

Cf. A000010, A049559, A330747.

Cf. also A344773.

Programs

PARI

A049559(n) = gcd(n-1, eulerphi(n));
A344774(n) = { my(x=A049559(n)); sumdiv(n,d,A049559(d)==x); };

Formula

a(n) = Sum_{d|n} [A049559(d) = A049559(n)], where [ ] is the Iverson bracket.

a(n) <= A330747(n).