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A301773
Number of odd chordless cycles in the 2n-Moebius ladder graph.
0
0, 4, 8, 16, 48, 124, 320, 844, 2208, 5776, 15128, 39604, 103680, 271444, 710648, 1860496, 4870848, 12752044, 33385280, 87403804, 228826128, 599074576, 1568397608, 4106118244, 10749957120, 28143753124, 73681302248, 192900153616, 505019158608, 1322157322204
OFFSET
0,2
COMMENTS
Sequence extended to a(0)-a(1) using the formula/recurrence.
LINKS
Eric Weisstein's World of Mathematics, Chordless Cycle
Eric Weisstein's World of Mathematics, Moebius Ladder
FORMULA
a(n) = A005248(n) - 2*cos(2*n*Pi/3).
a(n) = 2*a(n-1) + a(n-2) + 2*a(n-3) - a(n-4).
G.f.: -4*x*(x-1)*(1+x) / ( (x^2-3*x+1)*(1+x+x^2) ).
E.g.f.: 2*exp(-x/2)*(exp(2*x)*cosh(sqrt(5)*x/2) - cos(sqrt(3)*x/2)). - Stefano Spezia, Jul 21 2022
MATHEMATICA
Table[LucasL[2 n] - 2 Cos[2 n Pi/3], {n, 0, 20}]
LinearRecurrence[{2, 1, 2, -1}, {0, 4, 8, 16}, 20]
CoefficientList[Series[-4 x (-1 + x^2)/(1 - 2 x - x^2 - 2 x^3 + x^4), {x, 0, 20}], x]
CROSSREFS
Cf. A005248.
Sequence in context: A065978 A077447 A337783 * A102358 A038238 A230112
KEYWORD
nonn,easy
AUTHOR
Eric W. Weisstein, Mar 26 2018
STATUS
approved