A204391 Number of (n+2) X 3 0..1 arrays with no 3 X 3 subblock having three equal diagonal elements or three equal antidiagonal elements, and new values 0..1 introduced in row major order.

144, 648, 2952, 13448, 61336, 279752, 1276088, 5820872, 26552184, 121119048, 552490872, 2520216008, 11496098296, 52440058952, 239208098168, 1091160371912, 4977385663224, 22704607570248, 103568266524792, 472432117479368

Offset

1,1

Comments

Column 1 of A204398.

Links

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

Formula

Empirical: a(n) = 5*a(n-1) - 10*a(n-3) + 4*a(n-4).

Empirical g.f.: 8*x*(18 - 9*x - 36*x^2 + 16*x^3) / ((1 - 5*x + 2*x^2)*(1 - 2*x^2)). - Colin Barker, Jun 07 2018

Example

Some solutions for n=3:
..0..1..0....0..1..0....0..1..0....0..0..1....0..0..0....0..1..0....0..1..1
..0..1..1....0..1..0....0..0..1....1..0..0....1..1..1....1..0..1....0..1..1
..0..1..1....0..1..1....1..1..1....1..1..1....0..1..1....1..0..1....0..0..1
..0..1..1....1..1..0....0..1..0....0..1..0....0..1..0....0..1..1....0..0..1
..0..1..1....0..0..1....0..0..0....0..1..0....0..1..1....0..0..0....0..0..1

Crossrefs

Cf. A204398.

Sequence in context: A180413 A137885 A204398 * A233903 A233897 A250428

Adjacent sequences: A204388 A204389 A204390 * A204392 A204393 A204394

Keyword

nonn

Author

R. H. Hardin, Jan 15 2012

Status

approved