%I A066865
%S A066865 1,5,22,217,4726,164258,14840533,1834600977,669877863205,
%T A066865 296979228487760,434542100979981567
%N A066865 Number of binary arrangements without adjacent 1's on n X n staggered 
               hexagonal torus bent for odd n.
%D A066865 S. R. Finch, Mathematical Constants, Cambridge, 2003, pp. 342-349.
%D A066865 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.
%H A066865 S. R. Finch, <a href="http://algo.inria.fr/bsolve/constant/square/square.html">
               Hard Square Entropy Constant</a>
%e A066865 Neighbors for n=4: (The dots here represent spaces)
%e A066865 \|/ | \|/ |
%e A066865 -o--o--o--o-
%e A066865 .| /|\ | /|\
%e A066865 \|/ | \|/ |
%e A066865 -o--o--o--o-
%e A066865 .| /|\ | /|\
%e A066865 \|/ | \|/ |
%e A066865 -o--o--o--o-
%e A066865 .| /|\ | /|\
%e A066865 \|/ | \|/ |
%e A066865 -o--o--o--o-
%e A066865 .| /|\ | /|\
%e A066865 Neighbors for n=5:
%e A066865 \|/ | \|/ | \|/
%e A066865 .o--o--o--o--o
%e A066865 /| /|\ | /|\ |\
%e A066865 \|/ | \|/ | \|/
%e A066865 .o--o--o--o--o
%e A066865 /| /|\ | /|\ |\
%e A066865 \|/ | \|/ | \|/
%e A066865 .o--o--o--o--o
%e A066865 /| /|\ | /|\ |\
%e A066865 \|/ | \|/ | \|/
%e A066865 .o--o--o--o--o
%e A066865 /| /|\ | /|\ |\
%e A066865 \|/ | \|/ | \|/
%e A066865 .o--o--o--o--o
%e A066865 /| /|\ | /|\ |\
%o A066865 [S/R] proc a
%o A066865 stvar $[N][N]:boolean
%o A066865 init $[][] := false
%o A066865 cyset true
%o A066865 asgn $[][]->{false,true}
%o A066865 kill +[i in 0.. N-1](
%o A066865 +[j in 0.. N-1](
%o A066865 $[i][j]`*(
%o A066865 (
%o A066865 $[i][(j-1) mod N]`
%o A066865 +$[(i-1) mod N][j]`
%o A066865 +(
%o A066865 $[(i-1) mod N][(j-1) mod N]`
%o A066865 ? ((j mod 2)=0) |
%o A066865 $[(i+1) mod N][(j-1) mod N]`
%o A066865 )
%o A066865 ) ? ((j>0)+((N mod 2)=0)) | (
%o A066865 $[(i-1) mod N][j]`
%o A066865 +$[(i-1) mod N][(j-1) mod N]`
%o A066865 +$[(i+1) mod N][(j-1) mod N]` )))) end
%Y A066865 Cf. A006506 A027683 A066863 A066864 A066866, shifted instead of bent 
               A067967.
%Y A066865 Row sums of A067015.
%Y A066865 Sequence in context: A048252 A066866 A115657 this_sequence A005632 A002069 
               A120488
%Y A066865 Adjacent sequences: A066862 A066863 A066864 this_sequence A066866 A066867 
               A066868
%K A066865 nonn
%O A066865 1,2
%A A066865 Ron Hardin (rhhardin(AT)att.net), Jan 25, 2002