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%I #30 Mar 13 2021 15:14:32
%S 3,13,31,113,131,311,1113,1131,1311,3111,11113,11131,11311,13111,
%T 31111,111113,111131,111311,113111,131111,311111,1111113,1111131,
%U 1111311,1113111,1131111,1311111,3111111,11111113,11111131,11111311,11113111
%N Numbers with multiplicative digital root value 3.
%C Numbers with one 3, and zero or more 1s. - _Daniel Forgues_, Oct 09 2011
%H Robert Israel, <a href="/A034050/b034050.txt">Table of n, a(n) for n = 1..10000</a>
%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)/2 members up to 10^n, so a(n) is about 10^sqrt(2n).
%F a(m*(m-1)/2+j+1) = (10^m-1)/9 + 2*10^j for 0 <= j < m. - _Robert Israel_, Sep 27 2016
%p seq(seq((10^m-1)/9 + 2*10^j,j=0..m-1),m=1..10); # _Robert Israel_, Sep 27 2016
%t Sort[Flatten[Table[FromDigits/@Permutations[Join[{3},PadRight[{},n,1]]],{n,0,8}]]] (* _Harvey P. Dale_, Jul 16 2012 *)
%o (Python) # through 8-digit terms
%o print([int("1"*(d-i)+"3"+"1"*i) for d in range(8) for i in range(d+1)]) # _Michael S. Branicky_, Mar 13 2021
%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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