OFFSET
1,2
COMMENTS
Non-semiprimes k such that k+1 is a prime.
FORMULA
a(n)=A059456(n)-1.
MATHEMATICA
Select[Prime[Range[70]]-1, PrimeOmega[#]!=2&] (* Harvey P. Dale, Jan 14 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Apr 28 2010
EXTENSIONS
Entries checked by R. J. Mathar, May 06 2010
STATUS
approved