A207725 Number of n X 4 0..1 arrays avoiding 0 0 0 and 0 1 0 horizontally and 0 1 1 and 1 0 1 vertically.

9, 81, 169, 441, 1225, 2809, 6241, 14161, 31329, 68121, 148225, 321489, 693889, 1495729, 3222025, 6932689, 14907321, 32046921, 68873401, 147987225, 317944561, 683038225, 1467273025, 3151811881, 6770162961, 14542189281, 31235967169

Offset

1,1

Comments

Column 4 of A207729.

Links

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

Formula

Empirical: a(n) = 3*a(n-1) - 2*a(n-2) + 3*a(n-3) - 6*a(n-4) + 3*a(n-7) + a(n-8) - a(n-10).

Empirical g.f.: x*(9 + 54*x - 56*x^2 + 69*x^3 + 51*x^4 - 5*x^5 - 45*x^6 - x^8 - x^9) / ((1 - x)*(1 + x^2 - x^3)*(1 - x - x^3)*(1 - x - 2*x^2 - x^3)). - Colin Barker, Jun 25 2018

Example

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

Crossrefs

Cf. A207729.

Sequence in context: A207684 A207510 A208104 * A044260 A208109 A208841

Adjacent sequences: A207722 A207723 A207724 * A207726 A207727 A207728

Keyword

nonn

Author

R. H. Hardin, Feb 19 2012

Status

approved