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A067960 Number of binary arrangements without adjacent 1's on n X n torus connected ne-sw nw-se. 11
1, 9, 34, 961, 25531, 2722500, 464483559, 224546142769, 215560806324388, 509113406167679889, 2590618817013278596997, 30737628149641669227004804, 809724336154415150287031740151, 48754690373355654118816600200711441 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

If n is odd then A067960(n)=A027683(n-1).

a(18) = 2184710661251680812138610069332410066909052859790416601664, (a(17)=?). - Vaclav Kotesovec, Sep 16 2014

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 1..16

V. Kotesovec, Non-attacking chess pieces, 6ed, 2013, p. 440.

EXAMPLE

Neighbors for n=4 (dots represent spaces):

.\ /\ /\ /\ /

. o..o..o..o

./ \/ \/ \/ \

.\ /\ /\ /\ /

. o..o..o..o

./ \/ \/ \/ \

.\ /\ /\ /\ /

. o..o..o..o

./ \/ \/ \/ \

.\ /\ /\ /\ /

. o..o..o..o

./ \/ \/ \/ \

CROSSREFS

Cf. circle A000204, line A000045, arrays: ne-sw nw-se A067965, e-w ne-sw nw-se A067963, n-s nw-se A067964, e-w n-s nw-se A066864, e-w ne-sw n-s nw-se A063443, n-s A067966, e-w n-s A006506, nw-se A067962, toruses: bare A002416, ne-sw n-s nw-se A067959, e-w ne-sw n-s nw-se A067958, n-s A067961, e-w n-s A027683, e-w ne-sw n-s A066866.

Cf. A212271.

Sequence in context: A154393 A119389 A197273 * A119757 A003865 A265377

Adjacent sequences:  A067957 A067958 A067959 * A067961 A067962 A067963

KEYWORD

nonn,hard,nice

AUTHOR

R. H. Hardin, Feb 02 2002

EXTENSIONS

Terms a(12)-a(16) from Vaclav Kotesovec, May 18 2012.

STATUS

approved

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Last modified February 23 07:11 EST 2020. Contains 332159 sequences. (Running on oeis4.)