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 A053312 a(n) contains n digits (either '1' or '2') and is divisible by 2^n. 6
 2, 12, 112, 2112, 22112, 122112, 2122112, 12122112, 212122112, 1212122112, 11212122112, 111212122112, 1111212122112, 11111212122112, 211111212122112, 1211111212122112, 11211111212122112, 111211111212122112, 2111211111212122112, 12111211111212122112 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Alois P. Heinz, Table of n, a(n) for n = 1..1000 FORMULA 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. MATHEMATICA Select[Flatten[Table[FromDigits/@Tuples[{1, 2}, n], {n, 20}]], Divisible[ #, 2^IntegerLength[#]]&] (* Harvey P. Dale, Jul 01 2019 *) CROSSREFS Cf. A023396, A050621, A050622, A035014. Sequence in context: A316651 A330654 A091481 * A091854 A141141 A128571 Adjacent sequences:  A053309 A053310 A053311 * A053313 A053314 A053315 KEYWORD base,nonn AUTHOR Henry Bottomley, Mar 06 2000 STATUS approved

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Last modified April 5 23:16 EDT 2020. Contains 333260 sequences. (Running on oeis4.)