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 A291039 a(n) = (1/4)*A291038(n). 2
 1, 3, 8, 21, 54, 136, 337, 825, 2000, 4809, 11484, 27264, 64401, 151455, 354808, 828349, 1927986, 4475080, 10361441, 23936565, 55183904, 126983569, 291698040, 669004352, 1532095329, 3503889147, 8003207912, 18258464741, 41608726254, 94722900936, 215428701233 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Clark Kimberling, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (4, -4, 2, -4, 0, -1) FORMULA G.f.: -((-1 + x + x^3)/(-1 + 2 x + x^3)^2). a(n) = 4*a(n-1) - 4*a(n-2) + 2*a(n-3) - 4*a(n-4) - a(n-6) for n >= 7. MATHEMATICA z = 60; s = x/(x - x^3); p = (1 - 2 s)^2; Drop[CoefficientList[Series[s, {x, 0, z}], x], 1]  (* A079978  *) u = Drop[CoefficientList[Series[1/p, {x, 0, z}], x], 1]  (* A291038 *) u/4 (* A291039 *) CROSSREFS Cf. A079978, A290616, A291038. Sequence in context: A186812 A027930 A038200 * A030015 A318567 A103446 Adjacent sequences:  A291036 A291037 A291038 * A291040 A291041 A291042 KEYWORD nonn,easy AUTHOR Clark Kimberling, Sep 14 2017 STATUS approved

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Last modified December 16 04:22 EST 2019. Contains 330013 sequences. (Running on oeis4.)