OFFSET
1,2
COMMENTS
For each n, a(n) exists and is <= 5^(n-1).
LINKS
The Prime Puzzles & Problems Connection, Puzzle 376. n=p*2^x.
EXAMPLE
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.
MATHEMATICA
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}]
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Farideh Firoozbakht, Oct 27 2006
EXTENSIONS
Edited by Don Reble, Oct 29 2006
STATUS
approved