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 A121961 Expansion of g.f.: 1/( (1+2*x)*(1-2*x-4*x^2)*(1-2*x^2)^2 ). 1
 1, 0, 12, 8, 108, 160, 960, 2144, 9040, 24832, 89664, 270976, 916416, 2885120, 9500160, 30412288, 99084544, 319299584, 1035979776, 3347073024, 10842246144, 35064422400, 113514577920, 367253348352, 1188632055808, 3846143410176, 12447083347968, 40278203727872 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Based on characteristic polynomial of a square-within-a-square bonding graph. LINKS G. C. Greubel, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (0,12,8,-36,-32,32,32). FORMULA From G. C. Greubel, Oct 05 2019: (Start) a(2*n) = 4^(n+1)*(Fibonacci(2*n-2) + 1) - 2^n*(3*n-1). a(2*n+1) = 2^(2*n+3)*(Fibonacci(2*n-1) - 1) + 2^(n+2)*n. (End) MAPLE seq(coeff(series(1/((1-8*x^2-8*x^3)*(1-2*x^2)^2), x, n+1), x, n), n = 0 .. 40); # G. C. Greubel, Oct 05 2019 MATHEMATICA M = {{0, 1, 0, 1, 1, 0, 0, 1}, {1, 0, 1, 0, 1, 1, 0, 0}, {0, 1, 0, 1, 0, 1, 1, 0}, {1, 0, 1, 0, 0, 0, 1, 1}, {1, 1, 0, 0, 0, 0, 0, 0}, {0, 1, 1, 0, 0, 0, 0, 0}, {0, 0, 1, 1, 0, 0, 0, 0}, {1, 0, 0, 1, 0, 0, 0, 0}}; f[x_] = Det[M - x*IdentityMatrix[8]]; Table[ SeriesCoefficient[ Series[x/(x^10*f[1/x]), {x, 0, 30}], n], {n, 0, 30}] LinearRecurrence[{0, 12, 8, -36, -32, 32, 32}, {1, 0, 12, 8, 108, 160, 960}, 40] (* Harvey P. Dale, May 28 2017 *) Table[If[EvenQ[n], 4^(n/2 +1)*(Fibonacci[n-2] +1) - 2^(n/2)*(3*n/2 -1), 2^(n+2)*(Fibonacci[n-2] -1) + 2^((n+1)/2)*(n-1)], {n, 0, 40}] (* G. C. Greubel, Oct 05 2019 *) PROG (PARI) my(x='x+O('x^40)); Vec(1/((1-8*x^2-8*x^3)*(1-2*x^2)^2)) \\ G. C. Greubel, Oct 05 2019 (MAGMA) R:=PowerSeriesRing(Integers(), 40); Coefficients(R!( 1/((1-8*x^2-8*x^3)*(1-2*x^2)^2) )); // G. C. Greubel, Oct 05 2019 (Sage) def A121961_list(prec):     P. = PowerSeriesRing(ZZ, prec)     return P(1/((1-8*x^2-8*x^3)*(1-2*x^2)^2)).list() A121961_list(30) # G. C. Greubel, Oct 05 2019 (GAP) a:=[1, 0, 12, 8, 108, 160, 960];; for n in [8..40] do a[n]:=12*a[n-2] +8*a[n-3]-36*a[n-4]-32*a[n-5]+32*a[n-6]+32*a[n-7]; od; a; # G. C. Greubel, Oct 05 2019 CROSSREFS Cf. A000045. Sequence in context: A258641 A206478 A164675 * A168386 A338825 A338809 Adjacent sequences:  A121958 A121959 A121960 * A121962 A121963 A121964 KEYWORD nonn,easy AUTHOR Roger L. Bagula, Sep 02 2006 EXTENSIONS Edited by N. J. A. Sloane, Feb 01 2007 STATUS approved

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Last modified January 25 16:01 EST 2022. Contains 350572 sequences. (Running on oeis4.)