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A269915
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Number of ternary strings of length n with maximal run length three containing 1112.
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6
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1, 5, 21, 80, 287, 993, 3347, 11067, 36055, 116089, 370222, 1171353, 3681375, 11504101, 35772799, 110760185, 341640131, 1050254568, 3218970519, 9839399805, 30002862947, 91284474775, 277176264351, 840067321393, 2541769382014, 7678558044741, 23163047559031
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OFFSET
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4,2
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LINKS
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FORMULA
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G.f.: x^4*(x+1)*(x^2+1)*(x^2+x+1)/ ((x^6+3*x^5+5*x^4+5*x^3+3*x^2+x-1) * (2*x^3+2*x^2+2*x-1)).
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MATHEMATICA
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Drop[CoefficientList[Series[x^4 (x + 1) (x^2 + 1) (x^2 + x + 1)/((x^6 + 3 x^5 + 5 x^4 + 5 x^3 + 3 x^2 + x - 1) (2 x^3 + 2 x^2 + 2 x - 1)), {x, 0, 30}], x], 4] (* Michael De Vlieger, Mar 08 2016 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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