A236739 Number of (n+1) X (1+1) 0..2 arrays with the upper median plus the lower median of every 2 X 2 subblock equal.

81, 267, 833, 2907, 10233, 37467, 139201, 526395, 2012217, 7766523, 30188609, 118025307, 463513593, 1826935707, 7221598657, 28611883131, 113569804473, 451466339643, 1796832336449, 7158277169307, 28539550811769, 113856616625883

Offset

1,1

Links

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

Formula

Empirical: a(n) = 7*a(n-1) - 2*a(n-2) - 64*a(n-3) + 53*a(n-4) + 229*a(n-5) - 146*a(n-6) - 364*a(n-7) + 96*a(n-8) + 192*a(n-9).

Empirical g.f.: x*(81 - 300*x - 874*x^2 + 2794*x^3 + 4345*x^4 - 7738*x^5 - 10020*x^6 + 5472*x^7 + 6720*x^8) / ((1 - x)*(1 + x)*(1 - 4*x)*(1 - 3*x^2)*(1 - x - 4*x^2)*(1 - 2*x - 4*x^2)). - Colin Barker, Oct 21 2018

Example

Some solutions for n=5:
..2..0....1..2....1..2....0..2....0..2....1..1....0..2....1..1....1..0....0..1
..0..0....0..1....2..1....2..1....1..1....0..1....0..2....1..2....2..1....2..0
..1..0....1..1....2..0....1..2....0..2....1..2....1..1....1..0....1..1....1..0
..0..0....1..2....1..2....2..0....1..1....1..1....1..0....1..2....1..1....2..0
..0..0....1..1....2..1....2..1....0..2....0..1....1..1....1..1....1..2....1..0
..1..0....0..1....2..1....2..0....1..1....1..1....1..0....1..0....0..1....2..0

Crossrefs

Column 1 of A236746.

Sequence in context: A237637 A237630 A236746 * A237234 A237227 A206094

Adjacent sequences: A236736 A236737 A236738 * A236740 A236741 A236742

Keyword

nonn

Author

R. H. Hardin, Jan 30 2014

Status

approved