OFFSET
1,1
EXAMPLE
a(1)=9 because k=1 with prime factor 3 and 9+2=11, prime
MATHEMATICA
Contribution from Farideh Firoozbakht, Aug 12 2009: (Start)
a[n_]:=(c=Product[Prime[k], {k, 2, n+1}]; For[m=1, !(!PrimeQ[c(2m-1)]&&PrimeQ[c
(2m-1)+2]&&Length[FactorInteger[c(2m-1)]]==n), m++ ]; c(2m-1)); Table[a[n], {n, 17}] (End)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Enoch Haga, Dec 25 2007
EXTENSIONS
Edited, corrected and extended by Farideh Firoozbakht, Aug 12 2009
STATUS
approved