OFFSET
1,1
EXAMPLE
a(3) to a(5), 20 to 22, are a run of 3 consecutive numbers each having exactly 2 distinct prime divisors.
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Enoch Haga, Dec 09 2007
EXTENSIONS
Corrected and edited by R. J. Mathar, Dec 12 2007
STATUS
approved