A318840 a(n) = phi(n) - Product_{primes p dividing n} gcd(p-1, n-1).

0, 0, 0, 1, 0, 1, 0, 3, 4, 3, 0, 3, 0, 5, 4, 7, 0, 5, 0, 7, 8, 9, 0, 7, 16, 11, 16, 9, 0, 7, 0, 15, 16, 15, 20, 11, 0, 17, 20, 15, 0, 11, 0, 19, 16, 21, 0, 15, 36, 19, 28, 21, 0, 17, 36, 23, 32, 27, 0, 15, 0, 29, 32, 31, 32, 15, 0, 31, 40, 21, 0, 23, 0, 35, 36, 33, 56, 23, 0, 31, 52, 39, 0, 23, 48, 41, 52, 39, 0, 23, 36, 43, 56, 45, 68, 31

Offset: 1

Author

Antti Karttunen, Sep 11 2018

Keywords

• nonn

Links

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

Crossrefs

Cf. A000010, A063994, A318828, A318830.

Programs

PARI

A063994(n) = { my(f=factor(n)[,1]); prod(i=1, #f, gcd(f[i]-1, n-1)); };
A318840(n) = (eulerphi(n) - A063994(n));

Formula

a(n) = A000010(n) - A063994(n).

a(n) = A318828(n) - A051953(n).