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A231882
Number of maximal 2-independent sets in the planar 3 X n grid graph.
1
0, 3, 4, 11, 17, 36, 69, 133, 254, 499, 959, 1852, 3589, 6943, 13410, 25951, 50197, 97050, 187699, 363047, 702066, 1357755, 2625947, 5078438, 9821417, 18994465, 36734648, 71043261, 137395463, 265718350, 513889567, 993844901, 1922062694, 3717202293, 7188941039
OFFSET
0,2
LINKS
R. Euler, P. Oleksik, Z. Skupien, Counting Maximal Distance-Independent Sets in Grid Graphs, Discussiones Mathematicae Graph Theory. Volume 33, Issue 3, Pages 531-557, ISSN (Print) 2083-5892, July 2013; see also.
FORMULA
Euler et al. give an explicit g.f. and recurrence.
G.f.: x*(3 + x + 7*x^2 - 3*x^3 + 4*x^4 - 4*x^5 - x^6 - 2*x^7 - x^8) / ((1 + x)*(1 - 2*x + 2*x^2 - 5*x^3 + 4*x^4 - 4*x^5 + 3*x^6 - x^7 + x^8)). - Colin Barker, Oct 03 2017
MATHEMATICA
LinearRecurrence[{1, 0, 3, 1, 0, 1, -2, 0, -1}, {0, 3, 4, 11, 17, 36, 69, 133, 254, 499}, 40] (* Harvey P. Dale, Oct 05 2017 *)
CROSSREFS
Sequence in context: A324552 A143680 A058569 * A026753 A027222 A026380
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Nov 17 2013
EXTENSIONS
Terms a(10) and beyond from Andrew Howroyd, Jun 10 2017
STATUS
approved