A020869 Number of single component forests in Moebius ladder M_n.

34, 222, 1280, 6955, 36378, 185178, 923696, 4535991, 22000490, 105640634, 503067648, 2379006071, 11183747330, 52306745310, 243553038816, 1129612848795, 5221079904978, 24057393297286, 110543216068160, 506673892786803, 2317069421129034, 10574292843014802

Offset

2,1

Links

Colin Barker, Table of n, a(n) for n = 2..1000

J. P. McSorley, Counting structures in the Moebius ladder, Discrete Math., 184 (1998), 137-164.

Index entries for linear recurrences with constant coefficients, signature (13,-64,156,-218,190,-108,40,-9,1).

Formula

G.f.: x^2*(3x^8 - 27x^7 + 126x^6 - 360x^5 + 663x^4 - 781x^3 + 570x^2 - 220x + 34)/((1-x)^3*(1 - 5x + 3x^2 - x^3)^2). - Emeric Deutsch, Dec 21 2004

The McSorley reference gives the approximation a(n) ~ 0.8757*n*4.3652^n - 1.5432*n*0.4786^n*cos(0.8458*n+0.9674) + n^2 - 2*n. - Emeric Deutsch, Dec 21 2004

Maple

G:=x^2*(3*x^8-27*x^7+126*x^6-360*x^5+663*x^4-781*x^3+570*x^2-220*x+34)/(1-x)^3/(1-5*x+3*x^2-x^3)^2: Gser:=series(G, x=0, 27): seq(coeff(Gser, x^n), n=2..25); # Emeric Deutsch, Dec 21 2004

Prog

(PARI) Vec(-x^2*(3*x^8-27*x^7+126*x^6-360*x^5+663*x^4-781*x^3+570*x^2-220*x+34) / ((x-1)^3*(x^3-3*x^2+5*x-1)^2) + O(x^30)) \\ Colin Barker, Aug 01 2015

Crossrefs

Sequence in context: A302227 A058581 A050263 * A355884 A055716 A233300

Adjacent sequences: A020866 A020867 A020868 * A020870 A020871 A020872

Keyword

nonn,easy

Author

N. J. A. Sloane

Extensions

More terms from Emeric Deutsch, Dec 21 2004

Status

approved