OFFSET
1,1
FORMULA
tau(p^(2c)), where tau is the number of divisors, c > 1 and p is prime.
EXAMPLE
tau(p^(2c)) = 2c+1 is prime if c = (odd prime -1)/2 = 1, 2, 3, 5, 6, 8, ... = A005097.
MATHEMATICA
DivisorSigma[0, Select[Range[60000], ! PrimeQ[#] && PrimePowerQ[#] &]^2] (* Amiram Eldar, Apr 13 2024 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Nov 16 2001
EXTENSIONS
Name corrected by Amiram Eldar, Apr 13 2024
STATUS
approved