A280279 Number of n X 1 0..2 arrays with no element equal to more than one of its horizontal and vertical neighbors, with the exception of exactly one element, and with new values introduced in order 0 sequentially upwards.

0, 0, 1, 2, 8, 28, 94, 304, 960, 2976, 9096, 27488, 82304, 244544, 721888, 2119168, 6191104, 18011136, 52203648, 150809088, 434382848, 1247857664, 3576143360, 10226274304, 29184704512, 83138240512, 236438194176, 671370043392

Offset

1,4

Comments

Column 1 of A280284.

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 4*a(n-1) - 8*a(n-3) - 4*a(n-4) for n>7.

Empirical g.f.: x^3*(1 - 2*x + 4*x^3 + 2*x^4) / (1 - 2*x - 2*x^2)^2. - Colin Barker, Feb 19 2018

Example

All solutions for n=4:
..0. .0
..1. .0
..1. .0
..1. .1

Crossrefs

Cf. A280284.

Sequence in context: A178222 A090426 A279193 * A060995 A106731 A318010

Adjacent sequences: A280276 A280277 A280278 * A280280 A280281 A280282

Keyword

nonn

Author

R. H. Hardin, Dec 30 2016

Status

approved