OFFSET
1,2
COMMENTS
The union of {1}, the primes A000040, and powers of the form p^q where p and q are distinct primes.
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Dec 05 2009
EXTENSIONS
Attribute "power-free" removed from the definition by R. J. Mathar, Dec 09 2009
Inserted a(19)=43 by Gionata Neri, Dec 28 2015
STATUS
approved