OFFSET
1,1
COMMENTS
Here Omega(n) is the number of prime factors of n (with multiplicity), and tau(n) is the number of divisors of n. Thus this is the sequence of numbers n such that the denominator of 2 * Omega(n) * tau(n) / (Omega(n) + tau(n)) is prime.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
For 24 we have Omega(24) = 4 and tau(24) = 8. Thus 2 * 4 * 8/(4 + 8) = 64/12 = 16/3, hence 24 is in the sequence.
MAPLE
MATHEMATICA
Select[Range[100], PrimeQ[Denominator[2PrimeOmega[#]DivisorSigma[0, #]/(PrimeOmega[#] + DivisorSigma[0, #])]] &] (* Alonso del Arte, Aug 16 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Aug 15 2015
STATUS
approved