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A287498 Number of maximal independent vertex sets (and minimal vertex covers) in the n-web graph. 0
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 (list; graph; refs; listen; history; text; internal format)
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 * A174911 A032820 A197615

Adjacent sequences:  A287495 A287496 A287497 * A287499 A287500 A287501

KEYWORD

nonn,easy

AUTHOR

Eric W. Weisstein, May 25 2017

STATUS

approved

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Last modified December 6 16:24 EST 2019. Contains 329808 sequences. (Running on oeis4.)