A319696 Number of distinct values obtained when Euler phi (A000010) is applied to the divisors of n.

1, 1, 2, 2, 2, 2, 2, 3, 3, 2, 2, 3, 2, 2, 4, 4, 2, 3, 2, 4, 4, 2, 2, 4, 3, 2, 4, 4, 2, 4, 2, 5, 4, 2, 4, 5, 2, 2, 4, 5, 2, 4, 2, 4, 6, 2, 2, 5, 3, 3, 4, 4, 2, 4, 4, 6, 4, 2, 2, 5, 2, 2, 5, 6, 4, 4, 2, 4, 4, 4, 2, 7, 2, 2, 6, 4, 4, 4, 2, 6, 5, 2, 2, 6, 4, 2, 4, 6, 2, 6, 4, 4, 4, 2, 4, 6, 2, 3, 6, 6, 2, 4, 2, 6, 8

Offset: 1

Author

Antti Karttunen, Oct 02 2018

Keywords

• nonn

Examples

			For n = 6, it has four divisors: 1, 2, 3 and 6, and applying A000010 to these gives 1, 1, 2, 2, with just two distinct values, thus a(6) = 2.
		

Links

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

Crossrefs

Cf. A000010, A319695.

Cf. also A184395, A319686.

Programs

PARI

A319696(n) = { my(m=Map(),s,k=0); fordiv(n,d,if(!mapisdefined(m,s=eulerphi(d)), mapput(m,s,s); k++)); (k); };

Formula

a(n) = A319695(n) + [n (mod 4) != 2], where [ ] is the Iverson bracket, resulting 0 when n = 2 mod 4, and 1 otherwise.