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A066865 Number of binary arrangements without adjacent 1's on n X n staggered hexagonal torus bent for odd n. 4
1, 5, 22, 217, 4726, 164258, 14840533, 1834600977, 669877863205, 296979228487760, 434542100979981567 (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

Table of n, a(n) for n=1..11.

Steven R. Finch, Hard Square Entropy Constant [Broken link]

Steven R. Finch, Hard Square Entropy Constant [From the Wayback machine]

EXAMPLE

Neighbors for n=4: (The dots here represent spaces)

\|/ | \|/ |

-o--o--o--o-

.| /|\ | /|\

\|/ | \|/ |

-o--o--o--o-

.| /|\ | /|\

\|/ | \|/ |

-o--o--o--o-

.| /|\ | /|\

\|/ | \|/ |

-o--o--o--o-

.| /|\ | /|\

Neighbors for n=5:

\|/ | \|/ | \|/

.o--o--o--o--o

/| /|\ | /|\ |\

\|/ | \|/ | \|/

.o--o--o--o--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]`

+(

$[(i-1) mod N][(j-1) mod N]`

? ((j mod 2)=0) |

$[(i+1) mod N][(j-1) mod N]`

)

) ? ((j>0)+((N mod 2)=0)) | (

$[(i-1) mod N][j]`

+$[(i-1) mod N][(j-1) mod N]`

+$[(i+1) mod N][(j-1) mod N]` )))) end

CROSSREFS

Cf. A006506 A027683 A066863 A066864 A066866, shifted instead of bent A067967.

Row sums of A067015.

Sequence in context: A208804 A066866 A115657 * A183902 A005632 A183408

Adjacent sequences:  A066862 A066863 A066864 * A066866 A066867 A066868

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 25, 2002

STATUS

approved

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Last modified March 29 19:35 EDT 2020. Contains 333117 sequences. (Running on oeis4.)