OFFSET
1,1
FORMULA
A051802^-1(7)
MATHEMATICA
Select[Range[2500], NestWhile[Times@@(IntegerDigits[#]/.(0->1))&, #, #>9&] == 7&] (* Harvey P. Dale, Jan 18 2019 *)
CROSSREFS
KEYWORD
nonn,easy,base
AUTHOR
Dan Hoey, Dec 09 1999
STATUS
approved