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A319696
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Number of distinct values obtained when Euler phi (A000010) is applied to the divisors of n.
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9
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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
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OFFSET
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1,3
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LINKS
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FORMULA
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a(n) = A319695(n) + [n (mod 4) != 2], where [ ] is the Iverson bracket, resulting 0 when n = 2 mod 4, and 1 otherwise.
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EXAMPLE
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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.
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PROG
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(PARI) A319696(n) = { my(m=Map(), s, k=0); fordiv(n, d, if(!mapisdefined(m, s=eulerphi(d)), mapput(m, s, s); k++)); (k); };
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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