%I #8 Jul 10 2018 21:16:05

%S 21,38,57,58,71,81,127,148,164,181,188,195,204,208,209,212,232,244,

%T 249,250,251,252,267,269,270,300,317,326,356,357,382,398,407,409,416,

%U 417,420,447,448,453,471,479,480,481,492,502,505,528,530,548,554,561,570

%N Numbers n such that (10^(n+1) mod 9^(n+1))/(10^n mod 9^n)=10, or A139739(n+1)/A139739(n)=10.

%C Also, this is the set of numbers n such that 9*floor((10/9)^(n+1))==10*floor((10/9)^n) (cf. A065566). For proof see Mathar link.

%H Robert Israel, <a href="/A139768/b139768.txt">Table of n, a(n) for n = 1..10000</a>

%H R. J. Mathar, <a href="/A139768/a139768.txt">Proof of alternative characterization.</a>

%p Res:= NULL: count:= 0:

%p v:= 1:

%p for n from 2 while count < 100 do

%p u:= floor((10/9)^n);

%p if 9*u = 10*v then count:= count+1; Res:= Res, n-1 fi;

%p v:= u;

%p od:

%p Res; # _Robert Israel_, Jul 10 2018

%Y Cf. A139739, A065566.

%K nonn

%O 1,1

%A _Zak Seidov_ and _N. J. A. Sloane_, May 20 2008, May 24 2008