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A115102
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a(0)=2, a(1)=8, a(n)=a(n-1)+2*a(n-2).
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1
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2, 8, 12, 28, 52, 108, 212, 428, 852, 1708, 3412, 6828, 13652, 27308, 54612, 109228, 218452, 436908, 873812, 1747628, 3495252, 6990508, 13981012, 27962028, 55924052, 111848108, 223696212, 447392428, 894784852, 1789569708, 3579139412, 7158278828
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| Essentially 2 * A084214.
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (1,2).
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FORMULA
| G.f. (2+6*x)/( (1+x)*(1-2*x) ). a(n) = 2*A084214(n+1). - R. J. Mathar, Jun 14 2011
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MATHEMATICA
| M = {{0, 1, -1}, {-1, 0, 1}, {1, -1, 0}}; o[M_] = IdentityMatrix[3]*Flatten[Table[Table[If[n - m == 0, {}, M[[n, m]]^2 + M[[m, n]]^2], {n, 1, m}], {m, 1, 3}]]; M1 = M.M + o[M]; w[0] = {2, 3, 5}; w[n_] := w[n] = M1.w[n - 1] a0 = Table[w[n][[1]], {n, 0, 25}]
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CROSSREFS
| Cf. A078008, A014551, A001045.
Sequence in context: A135957 A107755 A027718 * A047174 A048074 A126775
Adjacent sequences: A115099 A115100 A115101 * A115103 A115104 A115105
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KEYWORD
| nonn,easy
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AUTHOR
| Roger Bagula (rlbagulatftn(AT)yahoo.com), Mar 02 2006
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EXTENSIONS
| Edited by N. J. A. Sloane (njas(AT)research.att.com), Dec 04 2006
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