This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A188200 #5 Mar 30 2012 17:22:57
%S A188200 17,21,25,42,67,81,96,101,149,162,173,202,243,303,324,346,404,405,486,
%T A188200 519,567,648,692,732,857,1189,1464,2199,4398,11644,18325,33774,34453,
%U A188200 37999,70348,92664,141557,256820,263412,326778,349484,526824,535754,579708,1461987,1519308,1621052,2688905,4650964,8027458,8198651,8374956,13504910,17858551,20002383,55640285,154513633,170801638
%N A188200 Base-9 Keith numbers.
%C A188200 Keith numbers are described in A007629. Base 9 appears to be unusually rich in Keith numbers. Why?
%e A188200 101 is here because, in base 9, 101 is 122 and applying the Keith iteration to this number produces the numbers 1, 2, 2, 5, 9, 16, 30, 55, 101. Note that the multiples 202, 303, and 404 are here also.
%t A188200 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[#,9]&]
%Y A188200 Cf. A007629 (base 10), A162724 (base 2), A187713 (base 5), A188195-A188199.
%K A188200 nonn,base
%O A188200 1,1
%A A188200 _T. D. Noe_, Mar 24 2011