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A128853
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a(n) = the number of positive divisors of n which are coprime to phi(n) = A000010(n).
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0
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1, 2, 2, 1, 2, 2, 2, 1, 1, 2, 2, 2, 2, 2, 4, 1, 2, 1, 2, 2, 2, 2, 2, 2, 1, 2, 1, 2, 2, 4, 2, 1, 4, 2, 4, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 1, 4, 2, 2, 1, 2, 2, 2, 2, 2, 4, 2, 2, 2, 1, 4, 4, 2, 2, 4, 4, 2, 1, 2, 2, 2, 2, 4, 2, 2, 2, 1, 2, 2, 2, 4, 2, 4, 2, 2, 2, 4, 2, 2, 2, 4, 2, 2, 1, 2, 1, 2, 4, 2, 2, 4
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| 12 is coprime to 4 positive integers (1,5,7 and 11) which are <= 12; so phi(12)=4. There are 2 divisors (1 and 3) of 12 that are coprime to 4. So a(12) = 2.
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MAPLE
| with(numtheory): a:=proc(n) local div, ct, j: div:=divisors(n): ct:=0: for j from 1 to tau(n) do if igcd(div[j], phi(n))=1 then ct:=ct+1 else fi od: ct; end: seq(a(n), n=1..140); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 17 2007
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CROSSREFS
| Sequence in context: A023671 A117535 A072463 * A136165 A134193 A085030
Adjacent sequences: A128850 A128851 A128852 * A128854 A128855 A128856
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KEYWORD
| nonn
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AUTHOR
| Leroy Quet Apr 16 2007
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EXTENSIONS
| More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 17 2007
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