OFFSET
1,3
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
The 6 positive divisors of 20 are 1,2,4,5,10,20. Of these, only 1 and 5 are coprime to d(20) = 6. So a(20) = 2.
MAPLE
with(numtheory): a:=proc(n) local div, ct, i: div:=divisors(n): ct:=0: for i from 1 to tau(n) do if igcd(div[i], tau(n))=1 then ct:=ct+1 else ct:=ct: fi od: ct; end: seq(a(n), n=1..140); # Emeric Deutsch, Apr 14 2007
MATHEMATICA
cpd[n_]:=Module[{ds=DivisorSigma[0, n]}, Count[Divisors[n], _?(CoprimeQ[ #, ds]&)]]; Array[cpd, 110] (* Harvey P. Dale, Apr 21 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Apr 13 2007
EXTENSIONS
More terms from Emeric Deutsch, Apr 14 2007
STATUS
approved