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A020881
Number of strong restricted edge-subgraphs in Moebius ladder M_n.
1
18, 102, 418, 2006, 8946, 41222, 187202, 855606, 3899538, 17794662, 81157858, 370232726, 1688782386, 7703577542, 35140060802, 160293673206, 731187195858
OFFSET
2,1
LINKS
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: A365107 A008528 A373316 * A285043 A223241 A197339
KEYWORD
nonn,more
AUTHOR
EXTENSIONS
a(6)-a(18) from Sean A. Irvine, Apr 30 2019
STATUS
approved