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 A125817 a(n) = ((1 + 3*sqrt(2))^n - (1 - 3*sqrt(2))^n)/(2*sqrt(2)). 2
 0, 3, 6, 63, 228, 1527, 6930, 39819, 197448, 1071819, 5500254, 29221431, 151947180, 800658687, 4184419434, 21980036547, 115095203472, 603851028243, 3164320515510, 16594108511151, 86981665785972, 456063176261511, 2390814670884546, 12534703338214779 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS G. C. Greubel, Table of n, a(n) for n = 0..1000 (terms 0..200 from T. D. Noe) Index entries for linear recurrences with constant coefficients, signature (2, 17). FORMULA From Philippe Deléham, Dec 12 2006: (Start) a(n) = 2*a(n-1) + 17*a(n-2), with a(0)=0, a(1)=3. G.f.: 3*x/(1-2*x-17*x^2). (End) MATHEMATICA Expand[Table[((1+3Sqrt[2])^n -(1-3Sqrt[2])^n)/(2Sqrt[2]), {n, 0, 30}]] (* Artur Jasinski *) LinearRecurrence[{2, 17}, {0, 3}, 30] (* T. D. Noe, Mar 28 2012 *) PROG (PARI) my(x='x+O('x^30)); concat([0], Vec(3*x/(1-2*x-17*x^2))) \\ G. C. Greubel, Aug 02 2019 (MAGMA) I:=[0, 3]; [n le 2 select I[n] else 2*Self(n-1) +17*Self(n-2): n in [1..30]]; // G. C. Greubel, Aug 02 2019 (Sage) (3*x/(1-2*x-17*x^2)).series(x, 30).coefficients(x, sparse=False) # G. C. Greubel, Aug 02 2019 (GAP) a:=[0, 3];; for n in [3..30] do a[n]:=2*a[n-1]+17*a[n-2]; od; a; # G. C. Greubel, Aug 02 2019 CROSSREFS Sequence in context: A137090 A137138 A215492 * A053948 A270745 A137091 Adjacent sequences:  A125814 A125815 A125816 * A125818 A125819 A125820 KEYWORD nonn AUTHOR Artur Jasinski, Dec 10 2006 STATUS approved

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Last modified October 22 19:53 EDT 2019. Contains 328319 sequences. (Running on oeis4.)