A020881 Number of strong restricted edge-subgraphs in Moebius ladder M_n.

18, 102, 418, 2006, 8946, 41222, 187202, 855606, 3899538, 17794662, 81157858, 370232726, 1688782386, 7703577542, 35140060802, 160293673206, 731187195858

Offset

2,1

Links

Table of n, a(n) for n=2..18.

Sean A. Irvine, Java program (github)

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

Formula

For large n, (3.2143)^n < a(n) < (6.4188)^n (Th. 23.1.) - C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 17 2005

Conjectures from Colin Barker, Dec 20 2019: (Start)

G.f.: 2*x^2*(9 + 33*x + 8*x^2 - 12*x^3) / ((1 + x)*(1 + 2*x)*(1 - 5*x + 2*x^2)).

a(n) = 2*a(n-1) + 11*a(n-2) + 4*a(n-3) - 4*a(n-4) for n>5.

(End)

Crossrefs

Sequence in context: A229326 A365107 A008528 * A285043 A223241 A197339

Adjacent sequences: A020878 A020879 A020880 * A020882 A020883 A020884

Keyword

nonn,more

Author

N. J. A. Sloane.

Extensions

a(6)-a(18) from Sean A. Irvine, Apr 30 2019

Status

approved