A237632 Number of (n+1) X (3+1) 0..2 arrays with the upper median of every 2 X 2 subblock differing from its horizontal and vertical neighbors by exactly one.

702, 1220, 1310, 1488, 2086, 2900, 4132, 5720, 8248, 11504, 16546, 22928, 33024, 46016, 66184, 91712, 132096, 184064, 264736, 366848, 528384, 736256, 1058944, 1467392, 2113536, 2945024, 4235776, 5869568, 8454144, 11780096, 16943104

Offset

1,1

Links

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

Formula

Empirical: a(n) = 4*a(n-4) for n>13.

Empirical g.f.: 2*x*(351 + 610*x + 655*x^2 + 744*x^3 - 361*x^4 - 990*x^5 - 554*x^6 - 116*x^7 - 48*x^8 - 48*x^9 + 9*x^10 + 24*x^11 + 16*x^12) / ((1 - 2*x^2)*(1 + 2*x^2)). - Colin Barker, Oct 24 2018

Example

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

Crossrefs

Column 3 of A237637.

Sequence in context: A252575 A252566 A269542 * A304155 A305508 A305174

Adjacent sequences: A237629 A237630 A237631 * A237633 A237634 A237635

Keyword

nonn

Author

R. H. Hardin, Feb 10 2014

Status

approved