A237631 Number of (n+1) X (2+1) 0..2 arrays with the upper median of every 2 X 2 subblock differing from its horizontal and vertical neighbors by exactly one.

260, 636, 1220, 2356, 4500, 8594, 16448, 31672, 60362, 116180, 223768, 429680, 822032, 1584164, 3047968, 5848520, 11216480, 21603248, 41526472, 79692176, 153032384, 294531296, 565871200, 1086330032, 2087379872, 4014989408

Offset

1,1

Links

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

Formula

Empirical: a(n) = 3*a(n-3) + 10*a(n-4) - 12*a(n-7) - 6*a(n-8) for n>12.

Empirical g.f.: 2*x*(130 + 318*x + 610*x^2 + 788*x^3 - 4*x^4 - 713*x^5 - 1410*x^6 - 1134*x^7 - 614*x^8 - 324*x^9 - 68*x^10 + 5*x^11) / (1 - 3*x^3 - 10*x^4 + 12*x^7 + 6*x^8). - Colin Barker, Oct 24 2018

Example

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

Crossrefs

Column 2 of A237637.

Sequence in context: A253504 A154379 A185793 * A202585 A037219 A290040

Adjacent sequences: A237628 A237629 A237630 * A237632 A237633 A237634

Keyword

nonn

Author

R. H. Hardin, Feb 10 2014

Status

approved