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A133673
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a(n) = n*L(n) + (n-1)*L(n-1) where L(n) is the Lucas number.
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1
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7, 18, 40, 83, 163, 311, 579, 1060, 1914, 3419, 6053, 10637, 18575, 32262, 55772, 96019, 164711, 281635, 480171, 816536, 1385262, 2345083, 3962185, 6682393, 11251543, 18916026, 31756624, 53243795, 89160619, 149135759, 249187923, 415946572, 693648930
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OFFSET
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2,1
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COMMENTS
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For n>2, two evens followed by four odds.
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LINKS
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FORMULA
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G.f.: -x^2*(-7-4*x+3*x^2+x^3)/(x^2+x-1)^2.
a(n) = 2*a(n-1)+a(n-2)-2*a(n-3)-a(n-4).
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EXAMPLE
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For n=2, a(2) = 7;
For n=21, a(21) = 816536.
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MATHEMATICA
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Total/@Partition[Times@@@Table[{n, LucasL[n]}, {n, 30}], 2, 1] (* or *) LinearRecurrence[{2, 1, -2, -1}, {7, 18, 40, 83}, 30](* Harvey P. Dale, Oct 21 2011 *)
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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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