OFFSET
1,2
LINKS
EXAMPLE
The Fibonacci numbers (A000045) start 0,1,1,2,3,5,8,13,21,..., so the first 1 is a term here, but the second 1 is not. (Note that 0 has infinitely many prime divisors.)
21 = 3 * 7 and 34 = 2 * 17 both have two prime factors, and because they are contiguous in the Fibonacci sequence, 21 is included.
CROSSREFS
KEYWORD
nonn
AUTHOR
Tomás Roca Sánchez, Oct 26 2019
EXTENSIONS
Edited to avoid confusion caused by the pair of 1's in the Fibonacci sequence. - N. J. A. Sloane, Nov 11 2019
STATUS
approved