OFFSET
1,2
LINKS
Jens Kruse Andersen, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = A079290(n) at least in the range n=3..94, and perhaps beyond. - R. J. Mathar, Aug 20 2014
Sum_{n>=1} 1/a(n) = 1/2 + Sum_{p prime} 1/(p*(p-1)) = 1/2 + A136141. - Amiram Eldar, Dec 21 2020
MATHEMATICA
Join[{1}, Select[Range[1, 20001, 2], PrimePowerQ[#]&&(!PrimeQ[#])&]] (* Harvey P. Dale, Dec 11 2018 *)
PROG
(Sage)
def isA244623(n) :
return(n % 2 == 1 and is_prime_power(n) == 1 and is_prime(n) == 0)
[n for n in (1..20000) if isA244623(n)]
(PARI) isok(p) = ((p%2) && !isprime(p) && isprimepower(p)) || (p==1); \\ Michel Marcus, Jul 06 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Jani Melik, Jul 02 2014
STATUS
approved