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A053312
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a(n) contains n digits (either '1' or '2') and is divisible by 2^n.
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8
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2, 12, 112, 2112, 22112, 122112, 2122112, 12122112, 212122112, 1212122112, 11212122112, 111212122112, 1111212122112, 11111212122112, 211111212122112, 1211111212122112, 11211111212122112, 111211111212122112, 2111211111212122112, 12111211111212122112
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OFFSET
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1,1
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LINKS
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Alois P. Heinz, Table of n, a(n) for n = 1..1000
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FORMULA
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a(n) = a(n-1)+10^(n-1)*(2-[a(n-1)/2^(n-1) mod 2]) i.e. a(n) ends with a(n-1); if (n-1)-th term is divisible by 2^n then n-th term begins with a 2, if not then n-th term begins with a 1.
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MATHEMATICA
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Select[Flatten[Table[FromDigits/@Tuples[{1, 2}, n], {n, 20}]], Divisible[ #, 2^IntegerLength[#]]&] (* Harvey P. Dale, Jul 01 2019 *)
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CROSSREFS
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Cf. A023396, A050621, A050622, A035014.
Sequence in context: A316651 A330654 A091481 * A091854 A141141 A128571
Adjacent sequences: A053309 A053310 A053311 * A053313 A053314 A053315
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KEYWORD
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base,nonn
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AUTHOR
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Henry Bottomley, Mar 06 2000
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STATUS
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approved
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