A251229 Number of (n+1) X (1+1) 0..3 arrays with every 2 X 2 subblock summing to 6 and no 2 X 2 subblock having exactly two nonzero entries.

38, 110, 322, 966, 2930, 8982, 27714, 85958, 267602, 835574, 2615266, 8202150, 25769714, 81093846, 255569538, 806554502, 2548769426, 8064427958, 25546995490, 81022985574, 257251995698, 817658450070, 2601529209282, 8285338752326

Offset

1,1

Links

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

Formula

Empirical: a(n) = 7*a(n-1) - 12*a(n-2) - 8*a(n-3) + 24*a(n-4).

Empirical g.f.: 2*x*(19 - 78*x + 4*x^2 + 168*x^3) / ((1 - 2*x)*(1 - 3*x)*(1 - 2*x - 4*x^2)). - Colin Barker, Nov 27 2018

Example

Some solutions for n=4:
..2..1....1..2....1..3....2..1....2..1....0..2....2..1....3..1....3..2....1..1
..3..0....3..0....1..1....1..2....1..2....1..3....3..0....0..2....1..0....2..2
..2..1....1..2....2..2....2..1....0..3....2..0....1..2....1..3....3..2....0..2
..1..2....1..2....1..1....2..1....1..2....3..1....0..3....1..1....0..1....3..1
..2..1....3..0....1..3....3..0....0..3....0..2....2..1....1..3....2..3....1..1

Crossrefs

Column 1 of A251236.

Sequence in context: A244177 A251236 A283804 * A282850 A173309 A044289

Adjacent sequences: A251226 A251227 A251228 * A251230 A251231 A251232

Keyword

nonn

Author

R. H. Hardin, Nov 30 2014

Status

approved