A285185 Expansion of (2*x+4*x^2) / (1-2*x-2*x^2+2*x^3).

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

Colin Barker, Table of n, a(n) for n = 0..1000

Tomislav Doslic, I. Zubac, Counting maximal matchings in linear polymers, Ars Mathematica Contemporanea 11 (2016) 255-276. See Prop. 4.11.

Index entries for linear recurrences with constant coefficients, signature (2,2,-2).

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

Adjacent sequences: A285182 A285183 A285184 * A285186 A285187 A285188

Keyword

nonn,easy

Author

N. J. A. Sloane, Apr 23 2017

Status

approved