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 A290493 Number of irredundant sets in the n-cycle graph. 2
 1, 3, 4, 11, 16, 24, 43, 75, 130, 218, 375, 644, 1106, 1893, 3244, 5563, 9538, 16350, 28026, 48046, 82366, 141199, 242053, 414948, 711341, 1219442, 2090470, 3583661, 6143419, 10531574, 18054122, 30949915, 53056986, 90954814, 155922503, 267295658, 458221025 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Eric Weisstein's World of Mathematics, Cycle Graph Eric Weisstein's World of Mathematics, Irredundant Set Index entries for linear recurrences with constant coefficients, signature (1, 1, 0, 1, 0, -1). FORMULA a(n) = a(n-1)+a(n-2)+a(n-4)-a(n-6). G.f.: (x (1 + 2 x + 4 x^3 - 6 x^5))/(1 - x - x^2 - x^4 + x^6). MATHEMATICA Table[RootSum[1 - #^2 - #^4 - #^5 + #^6 &, #^n &], {n, 20}] LinearRecurrence[{1, 1, 0, 1, 0, -1}, {1, 3, 4, 11, 16, 24}, 20] CoefficientList[Series[(1 + 2 x + 4 x^3 - 6 x^5)/(1 - x - x^2 - x^4 + x^6), {x, 0, 20}], x] CROSSREFS Sequence in context: A116654 A041020 A041527 * A266384 A248825 A001641 Adjacent sequences:  A290490 A290491 A290492 * A290494 A290495 A290496 KEYWORD nonn,easy AUTHOR Eric W. Weisstein, Aug 04 2017 STATUS approved

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Last modified May 14 10:15 EDT 2021. Contains 343880 sequences. (Running on oeis4.)