

A020881


Number of strong restricted edgesubgraphs in Moebius ladder M_n.


1



18, 102, 418, 2006, 8946, 41222, 187202, 855606, 3899538, 17794662, 81157858, 370232726, 1688782386, 7703577542, 35140060802, 160293673206, 731187195858
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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), 137164.


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(n1) + 11*a(n2) + 4*a(n3)  4*a(n4) for n>5.
(End)


CROSSREFS

Sequence in context: A107600 A229326 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



