OFFSET
3,1
LINKS
Eric Weisstein's World of Mathematics, Maximal Independent Vertex Set
Eric Weisstein's World of Mathematics, Minimal Vertex Cover
Eric Weisstein's World of Mathematics, Moebius Ladder
Index entries for linear recurrences with constant coefficients, signature (0,1,2,1).
FORMULA
a(n) = Lucas(n) - 2*cos(2*n*Pi/3).
a(n) = a(n-2) + 2*a(n-3) + a(n-4).
G.f.: -((2 x (1 + 4 x + 5 x^2 + 2 x^3))/(-1 + x^2 + 2 x^3 + x^4)).
MATHEMATICA
Table[LucasL[n] - 2 Cos[2 n Pi/3], {n, 3, 20}]
LinearRecurrence[{0, 1, 2, 1}, {2, 8, 12, 16}, 20]
CoefficientList[Series[-((2 (1 + 4 x + 5 x^2 + 2 x^3))/(-1 + x^2 + 2 x^3 + x^4)), {x, 0, 20}], x]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Eric W. Weisstein, Aug 07 2017
STATUS
approved