OFFSET
1,2
COMMENTS
49 = 7 * 7; 539 = 7 * 77; 5439 = 7 * 777.
MATHEMATICA
Module[{upto=3*10^6, sevs=Table[FromDigits[PadRight[{}, n, 7]], {n, 7}]}, Select[ Union[ Flatten[Table[Times@@@Tuples[sevs, i], {i, 7}]]], #<=upto&]] (* Harvey P. Dale, Feb 10 2015 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Claudio Meller, Jun 03 2009
EXTENSIONS
More terms from Claudio Meller, Jun 06 2009
STATUS
approved