OFFSET
4,1
COMMENTS
The wheel graph W_n has n vertices and 2n-2 edges. A single vertex is connected to all vertices of an (n-1)-cycle.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 4..1000
Eric Weisstein's World of Mathematics, Wheel Graph
Wikipedia, Wheel graph
Index entries for linear recurrences with constant coefficients, signature (5,-6,2).
FORMULA
G.f.: (38-56*x+20*x^2)*x^4 / (6*x^2+1-5*x-2*x^3).
a(n) = 2 * A035344(n-2).
MAPLE
a:= n-> `if`(n<4, 0, (Matrix([[5, 1, 0], [ -6, 0, 1], [2, 0, 0]])^n)[3, 2]): seq(a(n), n=4..30);
MATHEMATICA
CoefficientList[Series[((1 / x^4) (38 - 56 x + 20 x^2) x^4 / (6 x^2 + 1 - 5 x - 2 x^3)), {x, 0, 50}], x] (* Vincenzo Librandi, Jun 06 2013 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Mar 20 2009
STATUS
approved