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A034049
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Numbers with multiplicative digital root value 2.
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17
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2, 12, 21, 26, 34, 37, 43, 62, 73, 112, 121, 126, 134, 137, 143, 162, 173, 211, 216, 223, 232, 261, 278, 279, 287, 297, 299, 314, 317, 322, 341, 367, 369, 371, 376, 389, 396, 398, 413, 431, 447, 469, 474, 496, 612, 621, 637, 639, 649, 666, 673, 693, 694, 713
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OFFSET
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1,1
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LINKS
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Table of n, a(n) for n=1..54.
Eric Weisstein's World of Mathematics, Multiplicative Digital Root
Index entries for 10-automatic sequences.
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MATHEMATICA
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t = {}; n = 0; While[Length[t] < 100, n++; s = n; While[s > 10, s = Times @@ IntegerDigits[s]]; If[s == 2, AppendTo[t, n]]]; t (* T. D. Noe, Nov 15 2011 *)
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PROG
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(PARI) t(n) = {while(n>9, n=prod(i=1, #n=digits(n), n[i])); n};
for(n=0, 1e3, if(t(n) == 2, print1(n", "))); \\ Altug Alkan, Oct 19 2015
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CROSSREFS
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Cf. A031347.
Cf. A034048, A002275, A034049, A034050, A034051, A034052, A034053, A034054, A034055, A034056 (numbers having multiplicative digital roots 0-9).
Sequence in context: A231875 A031001 A048955 * A271361 A304813 A279424
Adjacent sequences: A034046 A034047 A034048 * A034050 A034051 A034052
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KEYWORD
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nonn,base
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AUTHOR
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Patrick De Geest, Sep 15 1998
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EXTENSIONS
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Incorrect formula removed by Martin Renner, Oct 19 2015
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STATUS
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approved
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