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A066866
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Number of binary arrangements without adjacent 1's in n X n rhombic hexagonal grid torus.
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12
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OFFSET
| 1,2
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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
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EXAMPLE
| neighbors for n=4:
.|/ |/ |/ |/
-o--o--o--o-
/| /| /| /|
.|/ |/ |/ |/
-o--o--o--o-
/| /| /| /|
.|/ |/ |/ |/
-o--o--o--o-
/| /| /| /|
.|/ |/ |/ |/
-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]`*(
$[i][(j+1) mod N]`
+$[(i-1) mod N][(j+1) mod N]`
+$[(i-1) mod N][j]` ))) end
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CROSSREFS
| Cf. A006506 A027683 A066863 A066864 A066865.
Sequence in context: A006294 A129437 A048252 * A115657 A066865 A183902
Adjacent sequences: A066863 A066864 A066865 * A066867 A066868 A066869
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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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