A020870 Number of strong single-component edge-subgraphs in Moebius ladder M_n.

38, 205, 1092, 5719, 29486, 150049, 755432, 3769771, 18673250, 91917621, 450025692, 2193031871, 10643233110, 51467250249, 248079277008, 1192335047635, 5715823515722, 27336235315037, 130457855039172, 621374856379623, 2954332179898174, 14023263123496049

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 (12,-50,88,-73,28,-4).

Formula

a(n) = n-1+[n(17-sqrt(17))/34+1][(5+sqrt(17))/2]^n+[n(17+sqrt(17))/34+1][(5-sqrt(17))/2]^n: G.f.: x^2(38-251x+532x^2-479x^3+192x^4-28x^5)/[(1-x)^2*(1-5x+2x^2)^2]. - Emeric Deutsch, Dec 21 2004

Maple

a:=n->(n*(17-sqrt(17))/34+1)*((5+sqrt(17))/2)^n+(n*(17+sqrt(17))/34+1)*((5-sqrt(17))/2)^n+n-1: seq(simplify(a(n)), n=2..24); # Emeric Deutsch, Dec 21 2004

Mathematica

LinearRecurrence[{12, -50, 88, -73, 28, -4}, {38, 205, 1092, 5719, 29486, 150049}, 30] (* Harvey P. Dale, May 08 2022 *)

Prog

(PARI) Vec(-x^2*(28*x^5-192*x^4+479*x^3-532*x^2+251*x-38)/((x-1)^2*(2*x^2-5*x+1)^2) + O(x^30)) \\ Colin Barker, Aug 01 2015

Crossrefs

Sequence in context: A281769 A191698 A124238 * A211502 A259518 A209250

Adjacent sequences: A020867 A020868 A020869 * A020871 A020872 A020873

Keyword

nonn,easy

Author

N. J. A. Sloane

Extensions

More terms from Emeric Deutsch, Dec 21 2004

Status

approved