A203103 Number of n X 3 binary arrays with every 1 immediately preceded by 0 0 to the left or above.

2, 4, 23, 90, 296, 1125, 4314, 15844, 58745, 219868, 818576, 3044097, 11340602, 42241116, 157267719, 585625606, 2180889380, 8121134761, 30241203842, 112613417592, 419352246749, 1561586350800, 5815059452328, 21654217951897

Offset

1,1

Comments

Column 3 of A203108.

Links

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

Formula

Empirical: a(n) = 2*a(n-1) +2*a(n-2) +15*a(n-3) +8*a(n-4) -4*a(n-5) -17*a(n-6) -12*a(n-7) -10*a(n-8) +5*a(n-9).

Empirical g.f.: x*(2 + 11*x^2 + 6*x^3 - 6*x^4 - 16*x^5 - 12*x^6 - 10*x^7 + 5*x^8) / (1 - 2*x - 2*x^2 - 15*x^3 - 8*x^4 + 4*x^5 + 17*x^6 + 12*x^7 + 10*x^8 - 5*x^9). - Colin Barker, Jun 04 2018

Example

Some solutions for n=5:
..0..0..1....0..0..0....0..0..0....0..0..0....0..0..0....0..0..1....0..0..0
..0..0..0....0..0..0....0..0..0....0..0..1....0..0..0....0..0..1....0..0..0
..1..1..0....0..0..0....1..0..0....0..0..1....0..0..1....0..0..0....0..0..1
..0..0..0....0..0..0....0..0..0....1..0..0....0..0..0....0..0..0....0..0..1
..0..0..1....0..0..1....0..0..0....0..1..0....1..1..0....0..0..1....1..1..0

Crossrefs

Cf. A203108.

Sequence in context: A018279 A307459 A133834 * A308164 A173352 A366224

Adjacent sequences: A203100 A203101 A203102 * A203104 A203105 A203106

Keyword

nonn

Author

R. H. Hardin, Dec 29 2011

Status

approved