A208380 Number of 4 X n 0..1 arrays avoiding 0 0 0 and 1 1 1 horizontally and 0 0 1 and 1 0 1 vertically.

8, 64, 108, 420, 1344, 4212, 13860, 44880, 144540, 468852, 1517184, 4906980, 15883764, 51401040, 166325292, 538259268, 1741843392, 5636673684, 18240740100, 59028275280, 191019298428, 618151779156, 2000381177088, 6473368570500

Offset

1,1

Comments

Row 4 of A208379.

Links

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

Formula

Empirical: a(n) = a(n-1) + 4*a(n-2) + 9*a(n-3) + 5*a(n-4) - 2*a(n-5) + 4*a(n-6) for n>8.

Empirical g.f.: 4*x*(2 + 14*x + 3*x^2 - 4*x^3 - 31*x^4 - 22*x^5 + 12*x^6 - 16*x^7) / ((1 - 2*x - 4*x^2)*(1 + x + 2*x^2 - x^3 + x^4)). - Colin Barker, Jul 02 2018

Example

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

Crossrefs

Cf. A208379.

Sequence in context: A136956 A345946 A161146 * A160428 A074102 A118719

Adjacent sequences: A208377 A208378 A208379 * A208381 A208382 A208383

Keyword

nonn

Author

R. H. Hardin, Feb 25 2012

Status

approved