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
KEYWORD
nonn,easy
AUTHOR
Eric W. Weisstein, Aug 04 2017
STATUS
approved