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A319696
Number of distinct values obtained when Euler phi (A000010) is applied to the divisors of n.
10
1, 1, 2, 2, 2, 2, 2, 3, 3, 2, 2, 3, 2, 2, 4, 4, 2, 3, 2, 4, 4, 2, 2, 4, 3, 2, 4, 4, 2, 4, 2, 5, 4, 2, 4, 5, 2, 2, 4, 5, 2, 4, 2, 4, 6, 2, 2, 5, 3, 3, 4, 4, 2, 4, 4, 6, 4, 2, 2, 5, 2, 2, 5, 6, 4, 4, 2, 4, 4, 4, 2, 7, 2, 2, 6, 4, 4, 4, 2, 6, 5, 2, 2, 6, 4, 2, 4, 6, 2, 6, 4, 4, 4, 2, 4, 6, 2, 3, 6, 6, 2, 4, 2, 6, 8
OFFSET
1,3
LINKS
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
Cf. also A184395, A319686.
Sequence in context: A349949 A196067 A251141 * A320111 A234287 A084294
KEYWORD
nonn
AUTHOR
Antti Karttunen, Oct 02 2018
STATUS
approved