OFFSET
1,1
COMMENTS
A152443(a(n)) is composite for all n.
EXAMPLE
There are 4 divisors of 27. These are 1,3,9,27. The proper divisors of 27 are therefore 1,3,9. The largest of these that is coprime to d(27) = 4 is 9. So a(27) = 9. (Note that in this case, the largest divisor of 27 coprime to 4 is 27, not 9.)
MATHEMATICA
a = {}; For[n = 2, n < 1000, n++, b = Max[Select[Drop[Divisors[n], -1], GCD[DivisorSigma[0, n], # ] == 1 &]]; If[b > 1 && ! PrimeQ[b], AppendTo[a, n]]]; a (* Stefan Steinerberger, Dec 06 2008 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Dec 04 2008
EXTENSIONS
Extended by Ray Chandler and Stefan Steinerberger, Dec 05 2008
STATUS
approved