OFFSET
0,2
MATHEMATICA
a = {}; Do[k = 1; While[ Count[ IntegerDigits[9^k], 7] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
Module[{nn=600, nk}, nk=Table[{n, DigitCount[9^n, 10, 7]}, {n, nn}]; Table[ SelectFirst[ nk, #[[2]]==k&], {k, 0, 50}]][[All, 1]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Nov 02 2019 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Robert G. Wilson v, Aug 10 2001
EXTENSIONS
Name corrected by Jon E. Schoenfield, Jun 26 2018
STATUS
approved