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A049680 a(n) = (L(n) + L(2*n))/2, where L = A000032 (the Lucas sequence). 2

%I

%S 2,2,5,11,27,67,170,436,1127,2927,7625,19901,52002,135982,355745,

%T 930931,2436527,6377807,16695530,43706576,114420627,299549527,

%U 784218605,2053091161,5375030402,14071960442,36840786845,96450296411

%N a(n) = (L(n) + L(2*n))/2, where L = A000032 (the Lucas sequence).

%H Indranil Ghosh, <a href="/A049680/b049680.txt">Table of n, a(n) for n = 0..2388</a>

%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4,-3,-2,1).

%F Binomial transform of trace(A^n)/4, where A is the adjacency matrix of path graph P_4 (A005248 with interpolated zeros). - _Paul Barry_, Apr 24 2004

%F From _George F. Johnson_, Feb 04 2013: (Start)

%F G.f.: (1-x)*(2-4*x-x^2)/ ( (1-x-x^2)*(1-3*x+x^2) ).

%F a(n) = 4*a(n-1) - 3*a(n-2) - 2*a(n-3) + a(n-4) for n>3. (End)

%e a(8) = (L(8) + L(2 * 8)) / 2 = (47 + 2207) / 2 = 2254 / 2 = 1127. - _Indranil Ghosh_, Feb 06 2017

%t LinearRecurrence[{4,-3,-2,1},{2,2,5,11},30] (* _Harvey P. Dale_, Nov 22 2015 *)

%t Table[(LuasL[n] + LucasL[2*n])/2, {n,0,30}] (* _G. C. Greubel_, Dec 02 2017 *)

%o (PARI) x='x+O('x^30); Vec((1-x)*(2-4*x-x^2)/ ( (1-x-x^2)*(1-3*x+x^2) )) \\ _G. C. Greubel_, Dec 02 2017

%o (MAGMA) [(Lucas(n) + Lucas(2*n)/2: n in [0..30]]; // _G. C. Greubel_, Dec 02 2017

%K nonn,easy

%O 0,1

%A _Clark Kimberling_

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Last modified May 25 03:14 EDT 2019. Contains 323539 sequences. (Running on oeis4.)