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A288920
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Number of 6-cycles in the n X n king graph.
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4
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0, 0, 82, 430, 1030, 1882, 2986, 4342, 5950, 7810, 9922, 12286, 14902, 17770, 20890, 24262, 27886, 31762, 35890, 40270, 44902, 49786, 54922, 60310, 65950, 71842, 77986, 84382, 91030, 97930, 105082, 112486, 120142, 128050, 136210, 144622, 153286, 162202
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OFFSET
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1,3
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LINKS
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FORMULA
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G.f.: 2*x^3*(41 + 92*x - 7*x^2) / (1 - x)^3.
a(n) = 550 - 534*n + 126*n^2 for n > 2.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n > 4. (End)
E.g.f.: 2*exp(x)*(275 - 204*x + 63*x^2) - 550 - 142*x + 7*x^2. - Stefano Spezia, Aug 14 2022
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MATHEMATICA
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Table[If[n < 3, 0, 2 (275 - 267 n + 63 n^2)], {n, 20}]
CoefficientList[Series[(2 x^2 (-41 - 92 x + 7 x^2))/(-1 + x)^3, {x, 0, 20}], x]
Join[{0, 0}, LinearRecurrence[{3, -3, 1}, {142, -14, 82}, {3, 20}]]
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PROG
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(PARI) concat(vector(2), Vec(2*x^3*(41 + 92*x - 7*x^2) / (1 - x)^3 + O(x^50))) \\ Colin Barker, Jun 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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