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 A066866 Number of binary arrangements without adjacent 1's in n X n rhombic hexagonal grid torus. 12
 1, 5, 22, 201, 4216, 162314, 12329633, 1831137521, 528106112383, 296848246952000, 324932515409958655, 692572885398506075946, 2874785146216927021053015 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES Steven 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. LINKS Steven R. Finch, Hard Square Entropy Constant [Broken link] Steven R. Finch, Hard Square Entropy Constant [From the Wayback machine] V. Kotesovec, Non-attacking chess pieces, 6ed, 2013, p. 73. EXAMPLE neighbors for n=4: .|/ |/ |/ |/ -o--o--o--o- /| /| /| /| .|/ |/ |/ |/ -o--o--o--o- /| /| /| /| .|/ |/ |/ |/ -o--o--o--o- /| /| /| /| .|/ |/ |/ |/ -o--o--o--o- /| /| /| /| 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 CROSSREFS Cf. A006506 A027683 A066863 A066864 A066865. Sequence in context: A129437 A048252 A208804 * A115657 A066865 A183902 Adjacent sequences:  A066863 A066864 A066865 * A066867 A066868 A066869 KEYWORD nonn,hard AUTHOR R. H. Hardin, Jan 25 2002 EXTENSIONS Terms a(11)-a(12) from Vaclav Kotesovec, May 07 2012 a(13) from Vaclav Kotesovec, Aug 15 2016 STATUS approved

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Last modified February 27 11:03 EST 2020. Contains 332304 sequences. (Running on oeis4.)