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A080920
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a(n) = 2a(n-1) + 35a(n-2), a(0)=0, a(1)=1.
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3
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0, 1, 2, 39, 148, 1661, 8502, 75139, 447848, 3525561, 22725802, 168846239, 1133095548, 8175809461, 56009963102, 398173257339, 2756695223248, 19449454453361, 135383241720402, 951497389308439, 6641408238830948
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OFFSET
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0,3
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LINKS
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FORMULA
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a(n) = 7^n/12 - (-5)^n/12.
a(n) = Sum{k=1..n, binomial(n, 2k-1)*6^(2(k-1))}.
G.f.: 1/((1+5x)(1-7x)).
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MATHEMATICA
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CoefficientList[Series[1 / ((1 + 5 x) (1 - 7 x)), {x, 0, 20}], x] (* Vincenzo Librandi, Aug 05 2013 *)
LinearRecurrence[{2, 35}, {0, 1}, 30] (* Harvey P. Dale, Aug 24 2017 *)
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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