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A284710
Number of maximal matchings in the n-Moebius ladder.
4
3, 3, 6, 23, 43, 102, 213, 447, 978, 2083, 4491, 9650, 20699, 44495, 95536, 205215, 440813, 946758, 2033611, 4367943, 9381882, 20151431, 43283105, 92967858, 199685543, 428904271, 921243300, 1978737343
OFFSET
1,1
COMMENTS
Recurrence used to extrapolate to a(1) and a(2).
LINKS
Eric Weisstein's World of Mathematics, Matching
Eric Weisstein's World of Mathematics, Maximal Independent Edge Set
Eric Weisstein's World of Mathematics, Moebius Ladder
FORMULA
a(n) = a(n-1)+2*a(n-2)+a(n-3)-a(n-4)+2*a(n-5)+a(n-6)-a(n-7)-a(n-8).
G.f.: x*(3-3*x^2+8*x^3+8*x^4+4*x^5-x^6-2*x^7)/(1-x-2*x^2-x^3+x^4-2*x^5-x^6+x^7+x^8).
MATHEMATICA
LinearRecurrence[{1, 2, 1, -1, 2, 1, -1, -1}, {3, 3, 6, 23, 43, 102, 213, 447, 978}, 30]
Table[2 Cos[n Pi/3] + RootSum[-1 - 2 # - #^2 + #^3 &, #^n &] - RootSum[-1 + #^2 + #^3 &, #^n &], {n, 3, 20}]
CROSSREFS
Sequence in context: A025256 A052560 A147836 * A377146 A019235 A222020
KEYWORD
nonn,easy
AUTHOR
Eric W. Weisstein, Apr 01 2017
STATUS
approved