A208014 Number of 4 X n 0..1 arrays avoiding 0 0 0 and 1 0 1 horizontally and 0 0 1 and 0 1 1 vertically.

9, 81, 225, 841, 2304, 6084, 18496, 53824, 150544, 435600, 1263376, 3610000, 10368400, 29899024, 85895824, 246741264, 709902736, 2041232400, 5866947216, 16869853456, 48507419536, 139454446096, 400947305616, 1152814510864

Offset

1,1

Comments

Row 4 of A208013.

Links

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

Formula

Empirical: a(n) = a(n-1) + 2*a(n-2) + 10*a(n-3) + 4*a(n-4) - 8*a(n-5) - 16*a(n-6) for n>8.

Empirical g.f.: x*(9 + 72*x + 126*x^2 + 364*x^3 + 167*x^4 - 404*x^5 - 714*x^6 - 148*x^7) / ((1 + 2*x^2 - 4*x^3)*(1 - x - 4*x^2 - 4*x^3)). - Colin Barker, Jun 26 2018

Example

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

Crossrefs

Cf. A208013.

Sequence in context: A208114 A208119 A207369 * A208556 A063824 A357450

Adjacent sequences: A208011 A208012 A208013 * A208015 A208016 A208017

Keyword

nonn

Author

R. H. Hardin, Feb 22 2012

Status

approved