OFFSET
1,1
COMMENTS
Integers greater than 1 and not in A109425.
LINKS
Enrique PĂ©rez Herrero, Table of n, a(n) for n = 1..10000
EXAMPLE
The number 36 is in the sequence because tau(36)=9 (1,2,3,4,6,9,12,18,36) and omega(36)=2 (2,3) and so tau(36)/omega(36)=9/2.
The number 12 is not in the sequence because tau(12)=6 (1,2,3,4,6,12) and omega(12)=2 (2,3) and so tau(12)/omega(12)=3.
MAPLE
with(numtheory): b:=proc(n) if type(tau(n)/nops(factorset(n)), integer)=false then n else fi end: seq(b(n), n=2..400);
MATHEMATICA
f[n_] := DivisorSigma[0, n]/Length[FactorInteger[n]]; Select[ Range[2, 369], !IntegerQ[ f[ # ]] &] (* Robert G. Wilson v, Jun 30 2005 *)
Select[Range[2, 400], !IntegerQ[DivisorSigma[0, #]/PrimeNu[#]]&] (* Harvey P. Dale, Oct 03 2015 *)
PROG
(PARI) is(n)=numdiv(n)%omega(n)>0 \\ Charles R Greathouse IV, May 15 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Emeric Deutsch, Jun 28 2005
STATUS
approved