OFFSET
1,1
EXAMPLE
a(1)=2 because 2 is a prime and prime(2)=3<(only one semiprime 4)<5=prime(2+1), a(2)=3 because 3 is a prime and prime(3)=5<(only one semiprime 6)<7=prime(3+1), a(3)=19 because 19 is a prime and prime(19)=67<(only one semiprime 69)<71=prime(19+1).
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Sep 17 2011
EXTENSIONS
Corrected by R. J. Mathar, Sep 20 2011
STATUS
approved