A287498 Number of maximal independent vertex sets (and minimal vertex covers) in the n-web graph.

0, 4, 9, 12, 30, 55, 105, 212, 405, 794, 1551, 3015, 5889, 11477, 22374, 43636, 85068, 165871, 323418, 630582, 1229517, 2397289, 4674198, 9113711, 17769780, 34647305, 67554891, 131717661, 256821477, 500747300

Offset

1,2

Links

Table of n, a(n) for n=1..30.

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, Web Graph

Index entries for linear recurrences with constant coefficients, signature (0,2,3,1).

Formula

G.f.: x^2*(-4 - 9*x - 4*x^2)/(-1 + 2*x^2 + 3*x^3 + x^4).

a(n) = 2*a(n-2) + 3*a(n-3) + a(n-4).

Mathematica

Table[RootSum[-1 - 3 # - 2 #^2 + #^4 &, #^n &], {n, 20}]
LinearRecurrence[{0, 2, 3, 1}, {0, 4, 9, 12}, 20]

Crossrefs

Sequence in context: A179808 A083351 A055381 * A359301 A174911 A032820

Adjacent sequences: A287495 A287496 A287497 * A287499 A287500 A287501

Keyword

nonn,easy

Author

Eric W. Weisstein, May 25 2017

Status

approved