OFFSET
1,1
COMMENTS
Numbers of the form p*q^k, where p and q are distinct primes and k>1.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
50 is in the sequence since it has exactly 2 semiprime divisors, 10 and 25.
MATHEMATICA
Select[Range[300], Length[(e = Sort[FactorInteger[#][[;; , 2]]])] == 2 && Min[e] == 1 && Max[e] > 1 &] (* Amiram Eldar, Sep 30 2021 *)
PROG
(Python)
from sympy import factorint
def ok(n):
e = sorted(factorint(n).values())
return len(e) == 2 and e[0] == 1 and e[1] > 1
print([k for k in range(276) if ok(k)]) # Michael S. Branicky, Dec 18 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Jun 16 2021
STATUS
approved