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A164406
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Number of binary strings of length n with no substrings equal to 0011 or 0101.
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2
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1, 2, 4, 8, 14, 24, 41, 68, 111, 180, 289, 460, 728, 1146, 1795, 2800, 4352, 6742, 10414, 16044, 24659, 37818, 57885, 88440, 134899, 205448, 312448, 474548, 719861, 1090734, 1650908, 2496260, 3770910, 5691360, 8582653, 12932512, 19472363, 29298540, 44053525
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = Sum_{i=0..floor((n+1)/2)} (n+1-2i) * C(n+1-2i,i). - Wesley Ivan Hurt, Nov 17 2017
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MATHEMATICA
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LinearRecurrence[{2, -1, 2, -2, 0, -1}, {14, 24, 41, 68, 111, 180}, 50] (* G. C. Greubel, Sep 19 2017 *)
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PROG
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(PARI) x='x+O('x^50); Vec((x^2+1)/(x^3+x-1)^2) \\ G. C. Greubel, Sep 19 2017
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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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EXTENSIONS
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STATUS
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approved
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