A067965 Number of binary arrangements without adjacent 1's on n X n array connected ne-sw and nw-se.

2, 9, 119, 2704, 177073, 21836929, 6985036032, 4576976735769, 7263963336910751, 24830487842030082304, 198126078679714777857441, 3494153303407491549112098721, 141264727800378056245286463971328, 12779122891585386852029424628087941481, 2628141044813862018744988536642011269669959

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

• Liang Kai, Table of n, a(n) for n = 1..27 (first 19 terms from Vaclav Kotesovec)
• Vaclav Kotesovec, Non-attacking chess pieces, 6ed, 2013, p. 69, 417.

Crossrefs

Main diagonal of A181212.

Cf. circle A000204, line A000045, arrays: 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 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.

Cf. A201861, A212271.

Extensions

Term a(14) from Vaclav Kotesovec, Dec 06 2011

Term a(15) from Vaclav Kotesovec, Jan 03 2012

Term a(16) from Vaclav Kotesovec, May 01 2012

Term a(17)-a(18) from Vaclav Kotesovec, Aug 13 2016