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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. 1
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified February 1 05:08 EST 2023. Contains 359981 sequences. (Running on oeis4.)