A111409 a(n) = f(f(n+1)) - f(f(n)), where f(0)=0, and for m>0, f(m) = phi(m) = A000010(m).

1, 0, 0, 0, 1, -1, 1, 0, 0, 0, 2, -2, 2, -2, 2, 0, 4, -6, 4, -2, 0, 0, 6, -6, 4, -4, 2, -2, 8, -8, 4, 0, 0, 0, 0, -4, 8, -6, 2, 0, 8, -12, 8, -4, 0, 2, 12, -14, 4, -4, 8, -8, 16, -18, 10, -8, 4, 0, 16, -20, 8, -8, 4, 4, 0, -8, 12, -4, 4, -12, 16, -16, 16, -12, 4, -4, 4, -8, 16, -8, 2, -2, 24, -32, 24, -20, 12, -8, 24, -32, 16, -4, -4, 6

Offset: 0

Author

N. J. A. Sloane, Nov 12 2005

Keywords

• sign

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A000010 (phi).

First differences of A010554.

Programs

Maple

a:= n-> (f-> f(f(n+1))-f(f(n)))(numtheory[phi]):
seq(a(n), n=0..100);  # Alois P. Heinz, Jun 20 2022

Extensions

Definition corrected by N. J. A. Sloane, Feb 14 2018