OFFSET
1,4
COMMENTS
The first odd number k with a(k) > 0 is k = 63.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = 0 if and only if n is in A326835.
a(2*n) > 0 for all n.
EXAMPLE
MATHEMATICA
f[n_] := Plus @@ DeleteDuplicates @ Map[EulerPhi, Divisors[n]]; a[n_] := Plus @@ Most @ FixedPointList[f, n] - n; Array[a, 100]
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Oct 07 2021
STATUS
approved