OFFSET
1,1
EXAMPLE
26 is a term because 26 = 2*13 and 2*26 - 1 = 51 = 3*17;
33 is a term because 33 = 3*11 and 2*33 - 1 = 65 = 5*13.
MATHEMATICA
f[n_]:=Last/@FactorInteger[n]=={1, 1}; lst={}; Do[If[f[n]&&f[2*n-1], AppendTo[lst, n]], {n, 0, 4*6!}]; lst
Select[Range[500], PrimeNu[#]==PrimeOmega[#]==PrimeNu[2#-1] == PrimeOmega[ 2#-1] == 2&] (* Harvey P. Dale, May 23 2014 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Joseph Stephan Orlovsky, May 04 2010
STATUS
approved