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%I #3 Oct 19 2017 03:15:04
%S 1,3,25,101,363,3125,15625,71023,390625,1183713,5474669,27151397,
%T 135646011,1220703125,6103515625,18480090517,85533990571,762939453125,
%U 3814697265625,11550150977337,53458791308981,265147974756053
%N a(n) is the smallest odd number m such that 2^n*m has n digits but has at most two distinct digits.
%C For each n, a(n) exists and is <= 5^(n-1).
%H The Prime Puzzles & Problems Connection, <a href="http://www.primepuzzles.net/puzzles/puzz_376.htm">Puzzle 376. n=p*2^x</a>.
%e a(13)=135646011 because 2^13*135646011=1111212122112 has 13 digits with two distinct digits and 135646011 is the smallest odd number m such that 2^13*m has these properties.
%t a[1]=1;a[n_]:=(For[m=Floor[5^(n-1)/4],!(Length[Union[IntegerDigits [2^n*(2m-1)]]]==2&&Length[IntegerDigits[2^n*(2m-1)]]==n),m++ ];2m-1 );Do[Print[a[n]],{n,14}]
%Y Cf. A124244.
%K nonn,base
%O 1,2
%A _Farideh Firoozbakht_, Oct 27 2006
%E Edited by _Don Reble_, Oct 29 2006
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