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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

Table of n, a(n) for n=1..37.

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.)