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A066863
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Number of binary arrangements without adjacent 1's on n X n staggered hexagonal grid.
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3
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2, 6, 43, 557, 14432, 719469, 70372090, 13351521479, 4941545691252, 3559349503024593, 4993739972681894885, 13642580224488264353504
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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REFERENCES
| S. R. Finch, Mathematical Constants, Cambridge, 2003, pp. 342-349.
J. Katzenelson and R. P. Kurshan, S/R: A Language for Specifying Protocols and Other Coordinating Processes, pp. 286-292 in Proc. IEEE Conf. Comput. Comm., 1986.
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LINKS
| S. R. Finch, Hard Square Entropy Constant
Eric Weisstein's World of Mathematics, Hard Hexagon Entropy Constant
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EXAMPLE
| Neighbors for n=4:
o--o--o--o
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o--o--o--o
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o--o--o--o
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o--o--o--o
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PROG
| [S/R] proc a
stvar $[N][N]:boolean
init $[][] := false
cyset true
asgn $[][]->{false, true}
kill +[i in 0.. N-1](
+[j in 0.. N-1](
$[i][j]`*(
($[i][j+1]`?(j<=N-2)|false)
+($[i-1][j-1]`?((i>0)*(j>0)*((j mod 2)=0))|false)
+($[i-1][j+1]`?((i>0)*(j<=N-2)*((j mod 2)=0))|false)
+($[i-1][j]`?(i>0)|false)))) end
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CROSSREFS
| Cf. A006506 A027683 A066864-A066866.
Sequence in context: A091241 A198076 A183313 * A135815 A055564 A077259
Adjacent sequences: A066860 A066861 A066862 * A066864 A066865 A066866
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KEYWORD
| nonn
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AUTHOR
| R. H. Hardin (rhhardin(AT)att.net), Jan 25, 2002
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