OFFSET
1,1
COMMENTS
Keith numbers are described in A007629.
EXAMPLE
57 is here because, in base 3, 57 is 2010 and applying the Keith iteration to this number produces the numbers 2, 0, 1, 0, 3, 4, 8, 15, 30, 57.
MATHEMATICA
IsKeith[n_, b_] := Module[{d, s, k}, d = IntegerDigits[n, b]; s = Total[d]; k = 1; While[AppendTo[d, s]; s = 2 s - d[[k]]; s < n, k++]; s == n]; Select[Range[3, 10^5], IsKeith[#, 3]&]
CROSSREFS
KEYWORD
nonn,base
AUTHOR
T. D. Noe, Mar 24 2011
STATUS
approved