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

1,1

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.

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

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.

Sequence in context: A386299 A075538 A395485 * A237999 A194017 A135543

Adjacent sequences: A067962 A067963 A067964 * A067966 A067967 A067968

Keyword

nonn,nice,hard

Author

R. H. Hardin, Feb 02 2002

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

Status

approved