OFFSET
1,1
LINKS
EXAMPLE
a(1)=65 because 3^4-2^4=65=5*13 is a semiprime; a(3)=19171: 3^9-2^9=19171=19*1009.
MATHEMATICA
Select[Table[3^n - 2^n, {n, 100}], PrimeOmega[#] == 2&] (* Vincenzo Librandi, Sep 21 2012 *)
PROG
(Magma) IsSemiprime:=func<n | &+[d[2]: d in Factorization(n)] eq 2>; [s: n in [2..100] | IsSemiprime(s) where s is 3^n - 2^n]; // Vincenzo Librandi, Sep 21 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
Hugo Pfoertner, Jun 03 2004
EXTENSIONS
a(10) from Vincenzo Librandi, Sep 21 2012
STATUS
approved