OFFSET
1,1
EXAMPLE
a(1)=3 because 3*3=semiprime(3) and 3=twin prime, a(2)=7 because 3*7=semiprime(7) and 3,7 are twin primes.
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, May 04 2010
EXTENSIONS
Entries checked and sequence extended beyond 139 - R. J. Mathar, May 06 2010
STATUS
approved