OFFSET
1,1
COMMENTS
Here but not in A062090: [729, 15625, 59049, 117649, 531441]; in A062090 but not here: [1, 6561, 390625]. - Klaus Brockhaus, Nov 01 2001
LINKS
T. D. Noe, Table of n, a(n) for n = 1..1000
FORMULA
Numbers of the form p^e where p is an odd prime and e+1 is a prime.
a(n) ~ n log n. - Charles R Greathouse IV, Aug 28 2013
EXAMPLE
Numbers of the form p^6 for example (such as 3^6 = 729) are here but not in A062090.
MATHEMATICA
Select[ Range[1, 250, 2], PrimeQ[ Length[ Divisors[ # ]]] & ]
Select[Range[1, 799, 2], PrimeQ[DivisorSigma[0, #]]&] (* Harvey P. Dale, Jun 22 2011 *)
PROG
(PARI) forstep(n=1, 1000, 2, if(isprime(numdiv(n)), print1(n, ", ")))
(PARI) is(n)=n%2 && isprime(isprimepower(n)+1) \\ Charles R Greathouse IV, Aug 28 2013
(Haskell)
a050150 n = a050150_list !! (n-1)
a050150_list = filter ((== 1) . a010051 . (+ 1) . a100995) [1, 3 ..]
-- Reinhard Zumkeller, Aug 16 2013
(Python)
from sympy import divisor_count, isprime
def ok(n): return n and n%2 and isprime(divisor_count(n))
print([k for k in range(250) if ok(k)]) # Michael S. Branicky, Jul 05 2022
CROSSREFS
KEYWORD
easy,nonn,nice
AUTHOR
Jason Earls, Jul 04 2001
EXTENSIONS
More terms from Jud McCranie, Oct 31 2001
STATUS
approved