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A285185
Expansion of (2*x+4*x^2) / (1-2*x-2*x^2+2*x^3).
2
0, 2, 8, 20, 52, 128, 320, 792, 1968, 4880, 12112, 30048, 74560, 184992, 459008, 1138880, 2825792, 7011328, 17396480, 43164032, 107098368, 265731840, 659332352, 1635931648, 4059064320, 10071327232, 24988919808, 62002365440, 153839916032, 381706723328, 947088547840, 2349910710272
OFFSET
0,2
LINKS
Tomislav Doslic, I. Zubac, Counting maximal matchings in linear polymers, Ars Mathematica Contemporanea 11 (2016) 255-276. See Prop. 4.11.
FORMULA
a(n) = 2*a(n-1) + 2*a(n-2) - 2*a(n-3) for n>2. - Colin Barker, Apr 23 2017
PROG
(PARI) concat(0, Vec(2*x*(1 + 2*x) / (1 - 2*x - 2*x^2 + 2*x^3) + O(x^30))) \\ Colin Barker, Apr 23 2017
CROSSREFS
Sequence in context: A146168 A058405 A133326 * A302323 A192698 A305050
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Apr 23 2017
STATUS
approved