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%I #20 Oct 06 2019 18:33:35
%S 9,19,33,91,119,133,191,313,331,911,1119,1133,1191,1313,1331,1911,
%T 3113,3131,3311,9111,11119,11133,11191,11313,11331,11911,13113,13131,
%U 13311,19111,31113,31131,31311,33111,91111,111119,111133,111191,111313,111331
%N Numbers with multiplicative digital root value 9.
%C Numbers with one 9 or two 3s, and zero or more 1s. - Daniel Forgues, Oct 09 2011
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/MultiplicativeDigitalRoot.html">Multiplicative Digital Root</a>
%H <a href="/index/Ar#10-automatic">Index entries for 10-automatic sequences</a>.
%F There are n(n+1)(n+2)/6 elements up to 10^n, so a(n) is about 10^sqrt(6n).
%Y Cf. A031347.
%Y Cf. A034048, A002275, A034049, A034050, A034051, A034052, A034053, A034054, A034055, A034056 (numbers having multiplicative digital roots 0-9).
%K nonn,base,easy
%O 1,1
%A _Patrick De Geest_, Sep 15 1998
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