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A128853
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a(n) is the number of positive divisors of n which are coprime to phi(n) = A000010(n).
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1
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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
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OFFSET
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1,2
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LINKS
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Antti Karttunen, Table of n, a(n) for n = 1..65537
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EXAMPLE
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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
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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, Apr 17 2007
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MATHEMATICA
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Table[Total[Boole[CoprimeQ[Divisors[n], EulerPhi[n]]]], {n, 120}] (* Harvey P. Dale, Oct 18 2020 *)
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PROG
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(PARI) A128853(n) = { my(ph=eulerphi(n)); sumdiv(n, d, (1==(gcd(d, ph)))); }; \\ Antti Karttunen, Sep 27 2018
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CROSSREFS
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Sequence in context: A214517 A230594 A072463 * A136165 A134193 A230259
Adjacent sequences: A128850 A128851 A128852 * A128854 A128855 A128856
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet, Apr 16 2007
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EXTENSIONS
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More terms from Emeric Deutsch, Apr 17 2007
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STATUS
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approved
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