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 A034049 Numbers with multiplicative digital root value 2. 17
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 Eric Weisstein's World of Mathematics, Multiplicative Digital Root Index entries for 10-automatic sequences. MAPLE A031347:= proc(n) local x; x:= n; while x > 10 do x:= convert(convert(x, base, 10), `*`) od; x end proc: select(A031347=2, [\$1..1000]); # Robert Israel, Jan 23 2023 MATHEMATICA 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 *) PROG (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 CROSSREFS Cf. A031347. Cf. A034048, A002275, A034049, A034050, A034051, A034052, A034053, A034054, A034055, A034056 (numbers having multiplicative digital roots 0-9). Sequence in context: A369303 A031001 A048955 * A271361 A304813 A279424 Adjacent sequences: A034046 A034047 A034048 * A034050 A034051 A034052 KEYWORD nonn,base AUTHOR Patrick De Geest, Sep 15 1998 EXTENSIONS Incorrect formula removed by Martin Renner, Oct 19 2015 STATUS approved

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Last modified September 15 11:45 EDT 2024. Contains 375938 sequences. (Running on oeis4.)