A334196 a(1) = 0, then after the first differences of A003434.

0, 1, 1, 0, 1, -1, 1, 0, 0, 0, 1, -1, 1, -1, 1, 0, 1, -2, 1, 0, 0, 0, 1, -1, 1, -1, 0, 0, 1, -1, 1, 0, 0, 0, 0, -1, 1, -1, 1, 0, 1, -2, 1, 0, 0, 0, 1, -1, 0, 0, 1, -1, 1, -2, 2, -1, 0, 0, 1, -1, 1, -1, 0, 1, 0, -1, 1, 0, 0, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, 0, -1, 1, 1, -2, 2, -2, 1, 0, 1, -2, 1, 0, 0, 0, 0, 0, 1, -2, 1, 0, 1, -1, 1, -1, 0

Offset: 1

Author

Antti Karttunen, Apr 18 2020

Keywords

• sign

Comments

Also, from a(2) onward the first differences of A049108, and from a(3) onward the first differences of A032358.

Links

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

Crossrefs

Cf. A000010, A003434, A032358, A049108, A334195.

Programs

Mathematica

Differences[Array[Length[FixedPointList[EulerPhi, #]] &, 100, 0]] (* Paolo Xausa, Aug 18 2024 *)

PARI

A003434(n) = for(k=0, n, n>1 || return(k); n=eulerphi(n));
A334196(n) = if(1==n,0,A003434(n)-A003434(n-1));

Formula

a(1) = 0; and for n > 1, a(n) = A003434(n) - A003434(n-1).