A290493 Number of irredundant sets in the n-cycle graph.

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

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