OFFSET
1,1
EXAMPLE
17-1=2^4, 1297-1=2^4*3^4, 1336337-1=2^4*17^4, 4477457-1=2^4*23^4,...
MATHEMATICA
Select[Table[Prime[n], {n, 600000}], Length[Union[Last/@FactorInteger[#-1]]]==1&&Union[Last/@FactorInteger[#-1]]=={4}&]
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Joseph Stephan Orlovsky, Apr 09 2011
EXTENSIONS
a(11)-a(21) from Donovan Johnson, Apr 10 2011
STATUS
approved