OFFSET
1,1
COMMENTS
This is to Lucky numbers (A000959) greater than 1, as semiprimes (A001358) are to primes (A000040). Since A000959(1) = 1, dropping the word "nontrivial" gives "product of two lucky numbers" = {a(i)} UNION A000959 = {1, 3, 7, 9, 13, 15, 21, 25, 27, 31, 33, 37, 39, 43, 45, 49, 51, 63, 67, 69, 73, 75, 79, 81, 87, 91, 93, 99, ...}.
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, May 05 2007
EXTENSIONS
99 =3*33 and 175 inserted, sequence extended - R. J. Mathar, Oct 22 2010
STATUS
approved