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A166542
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a(n) = 6*n - a(n-1), with n>1, a(1)=2.
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1
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2, 10, 8, 16, 14, 22, 20, 28, 26, 34, 32, 40, 38, 46, 44, 52, 50, 58, 56, 64, 62, 70, 68, 76, 74, 82, 80, 88, 86, 94, 92, 100, 98, 106, 104, 112, 110, 118, 116, 124, 122, 130, 128, 136, 134, 142, 140, 148, 146, 154, 152, 160, 158, 166, 164, 172, 170, 178, 176, 184
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OFFSET
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1,1
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LINKS
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FORMULA
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E.g.f.: (1/2)*(3*(1 + 2*x)*exp(x) + 5*exp(-x) - 8).
a(n) = a(n-1) + a(n-2) - a(n-3). (End)
Sum_{n>=1} (-1)^(n+1)/a(n) = 1/4 + Pi/(6*sqrt(3)). - Amiram Eldar, Feb 23 2023
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MATHEMATICA
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CoefficientList[Series[-(- 2 - 8 x + 4 x^2)/((1 + x) (x - 1)^2), {x, 0, 80}], x] (* Vincenzo Librandi, Sep 13 2013 *)
LinearRecurrence[{1, 1, -1}, {2, 10, 8}, 50] (* G. C. Greubel, May 16 2016 *)
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PROG
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(Magma) [n eq 1 select 2 else 6*n-Self(n-1): n in [1..80]]; // Vincenzo Librandi, Sep 13 2013
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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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