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 A188200 Base-9 Keith numbers. 7
 17, 21, 25, 42, 67, 81, 96, 101, 149, 162, 173, 202, 243, 303, 324, 346, 404, 405, 486, 519, 567, 648, 692, 732, 857, 1189, 1464, 2199, 4398, 11644, 18325, 33774, 34453, 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Keith numbers are described in A007629. Base 9 appears to be unusually rich in Keith numbers. Why? LINKS EXAMPLE 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. 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[#, 9]&] CROSSREFS Cf. A007629 (base 10), A162724 (base 2), A187713 (base 5), A188195-A188199. Sequence in context: A166875 A282109 A128546 * A060875 A259555 A138600 Adjacent sequences:  A188197 A188198 A188199 * A188201 A188202 A188203 KEYWORD nonn,base AUTHOR T. D. Noe, Mar 24 2011 STATUS approved

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