OFFSET
1,3
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..65537
FORMULA
a(n) = A319695(n) + [n (mod 4) != 2], where [ ] is the Iverson bracket, resulting 0 when n = 2 mod 4, and 1 otherwise.
EXAMPLE
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.
PROG
(PARI) A319696(n) = { my(m=Map(), s, k=0); fordiv(n, d, if(!mapisdefined(m, s=eulerphi(d)), mapput(m, s, s); k++)); (k); };
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Oct 02 2018
STATUS
approved