A067963 Number of binary arrangements without adjacent 1's on n X n array connected e-w ne-sw nw-se.

2, 7, 77, 1152, 56549, 3837761, 806190208, 251170142257, 223733272186825, 319544298135448960, 1210302996752248488817, 7876274672755293629849313, 127662922218147601317696761088, 3758866349549535184419575245899295

Offset: 1

Author

R. H. Hardin, Feb 02 2002

Keywords

• nonn
• nice
• hard

Examples

			Neighbors for n=4 (dots represent spaces):
. o--o--o--o
...\/ \/ \/
.../\ /\ /\
. o--o--o--o
...\/ \/ \/
.../\ /\ /\
. o--o--o--o
...\/ \/ \/
.../\ /\ /\
. o--o--o--o
		

Links

• R. H. Hardin and Vaclav Kotesovec, Table of n, a(n) for n = 1..30
• V. Kotesovec, Non-attacking chess pieces, 6ed, 2013, p. 69-71.

Crossrefs

Cf. circle A000204, line A000045, arrays: ne-sw nw-se A067965, 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 nw-se A067960, 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.

Diagonal of A228683

Extensions

Terms a(15)-a(19) from Vaclav Kotesovec, May 01 2012