A207147 Number of (n+1) X 7 0..2 arrays with every 2 X 2 subblock having nonzero determinant and commuting with every horizontal or vertical neighbor.

122, 187, 218, 374, 434, 754, 866, 1490, 1730, 2962, 3458, 5906, 6914, 11810, 13826, 23618, 27650, 47234, 55298, 94466, 110594, 188930, 221186, 377858, 442370, 755714, 884738, 1511426, 1769474, 3022850, 3538946, 6045698, 7077890, 12091394

Offset

1,1

Comments

Column 6 of A207149.

Links

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

Formula

Empirical: a(n) = a(n-1) + 2*a(n-2) - 2*a(n-3) for n>13.

Empirical g.f.: x*(122 + 65*x - 213*x^2 + 26*x^3 - 2*x^4 + 8*x^5 - 8*x^6 - 16*x^7 + 16*x^8 - 16*x^9 + 16*x^10 - 16*x^11 + 16*x^12) / ((1 - x)*(1 - 2*x^2)). - Colin Barker, Jun 19 2018

Example

Some solutions for n=4:
..2..0..2..0..1..0..2....1..2..0..2..0..1..0....2..0..1..0..1..0..1
..0..2..0..2..0..1..0....1..0..2..0..2..0..1....0..2..0..1..0..1..0
..1..0..2..0..2..0..1....0..1..0..2..0..2..0....2..0..2..0..1..0..1
..0..1..0..2..0..2..0....1..0..1..0..2..0..2....0..2..0..2..0..1..0
..2..0..1..0..2..0..2....0..1..0..1..0..2..2....1..0..2..0..2..0..1

Crossrefs

Cf. A207149.

Sequence in context: A309760 A224606 A224599 * A222578 A105983 A356369

Adjacent sequences: A207144 A207145 A207146 * A207148 A207149 A207150

Keyword

nonn

Author

R. H. Hardin, Feb 15 2012

Status

approved