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A269268
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Kolakoski-(1,5) sequence: a(n) is length of n-th run.
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6
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1, 5, 5, 5, 5, 5, 1, 1, 1, 1, 1, 5, 5, 5, 5, 5, 1, 1, 1, 1, 1, 5, 5, 5, 5, 5, 1, 5, 1, 5, 1, 5, 5, 5, 5, 5, 1, 1, 1, 1, 1, 5, 5, 5, 5, 5, 1, 1, 1, 1, 1, 5, 5, 5, 5, 5, 1, 5, 1, 5, 1, 5, 5, 5, 5, 5, 1, 1, 1, 1, 1, 5, 5, 5, 5, 5, 1, 1, 1, 1, 1, 5, 5, 5, 5, 5, 1
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OFFSET
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1,2
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COMMENTS
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15555511, 155555111, 155555111115555511111 are primes.
The fraction of 5s in this sequence approaches ((3+2*sqrt(2))^(1/3)+(3-2*sqrt(2))^(1/3))/4 ~ 0.588825 -- see the formula in A064353. - Ed Wynn, Sep 04 2019
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LINKS
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MATHEMATICA
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seed = {1, 5}; w = {}; i = 1; Do[w = Join[w, Array[seed[[Mod[i - 1, Length[seed]] + 1]] &, If[i > Length[w], seed, w][[i]]]]; i++, {n, 250}]; w (* from Ivan Neretin in similar sequences *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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