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4, 26, 180, 1258, 8804, 61626, 431380, 3019658, 21137604, 147963226, 1035742580, 7250198058, 50751386404, 355259704826, 2486817933780, 17407725536458, 121854078755204, 852978551286426, 5970849859004980, 41795949013034858
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listen;
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OFFSET
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0,1
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LINKS
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FORMULA
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a(n) = 7*a(n-1)-2.
a(n) = 8*a(n-1)-7*a(n-2).
G.f.: 2*(2-3*x)/((1-x)*(1-7*x)).
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MATHEMATICA
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\(11 7^Range[0, 20]+1)/3 (* or *) LinearRecurrence[{8, -7}, {4, 26}, 20] (* Harvey P. Dale, Aug 01 2020 *)
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PROG
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(Magma) [(11*7^n+1)/3: n in [0..30]];
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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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STATUS
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approved
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