OFFSET
1,1
FORMULA
A051802^-1(4)
MATHEMATICA
mdr4Q[n_]:=NestWhile[Times@@(IntegerDigits[#]/.(0->1))&, n, #>9&]==4; Select[ Range[ 400], mdr4Q] (* Harvey P. Dale, Jul 02 2021 *)
CROSSREFS
KEYWORD
nonn,easy,base
AUTHOR
Dan Hoey, Dec 09 1999
STATUS
approved