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A124245
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a(n) is the smallest odd number m such that 2^n*m has n digits but has at most two distinct digits.
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1
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1, 3, 25, 101, 363, 3125, 15625, 71023, 390625, 1183713, 5474669, 27151397, 135646011, 1220703125, 6103515625, 18480090517, 85533990571, 762939453125, 3814697265625, 11550150977337, 53458791308981, 265147974756053
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| For each n, a(n) exists and is <= 5^(n-1).
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LINKS
| The Prime Puzzles & Problems Connection, Puzzle 376. n=p*2^x.
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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.
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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}]
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CROSSREFS
| Cf. A124244.
Sequence in context: A075306 A183761 A180324 * A166899 A201534 A059457
Adjacent sequences: A124242 A124243 A124244 * A124246 A124247 A124248
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KEYWORD
| nonn,base
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AUTHOR
| Farideh Firoozbakht (mymontain(AT)yahoo.com), Oct 27 2006
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EXTENSIONS
| Edited by Don Reble (djr(AT)nk.ca), Oct 29 2006
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