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 A022303 The sequence a of 1's and 2's starting with (1,2,1) such that a(n) is the length of the (n+2)nd run of a. 11
 1, 2, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 1, 1, 2, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 2, 2, 1, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 2, 2, 1, 2, 1, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Clark Kimberling, Table of n, a(n) for n = 1..20000 EXAMPLE a(1) =1, so the 3rd run has length 1, so a(4) must be 2. a(2) = 2, so the 4th run has length 2, so a(5) = 2 and a(6) = 1. a(3) = 1, so the 5th run has length 1, so a(7) = 2. a(4) = 2, so the 6th run has length 2, so a(8) = 1 and a(9) = 1. Globally, the runlength sequence of a is 1,1,1,2,1,2,2,1,2,2,1,1,2,1,...., and deleting the first two terms leaves a = A022303. MATHEMATICA a = {1, 2}; Do[a = Join[a, ConstantArray[If[Last[a] == 1, 2, 1], {a[[n]]}]], {n, 100}]; a (* Peter J. C. Moses, Apr 02 2016 *) CROSSREFS Cf. A022300, A006928, A000002. Sequence in context: A308186 A107362 A166332 * A113189 A143098 A225515 Adjacent sequences:  A022300 A022301 A022302 * A022304 A022305 A022306 KEYWORD nonn AUTHOR EXTENSIONS Clarified and augmented by Clark Kimberling, Apr 02 2016 STATUS approved

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Last modified September 18 16:49 EDT 2021. Contains 347531 sequences. (Running on oeis4.)