A205513 Number of (n+1) X 2 0..2 arrays with the number of clockwise edge increases in every 2 X 2 subblock differing from each horizontal or vertical neighbor.

81, 360, 1683, 7572, 35577, 160218, 750426, 3387924, 15834846, 71633088, 334163931, 1514409882, 7052640282, 32013216726, 148862055267, 676669161648, 3142331422251, 14301747527646, 66336358731993, 302253567013566

Offset

1,1

Comments

Column 1 of A205520.

Links

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

Formula

Empirical: a(n) = 18*a(n-2) +6*a(n-3) +39*a(n-4) -2*a(n-5) -3*a(n-6) -4*a(n-7).

Empirical g.f.: 3*x*(27 + 120*x + 75*x^2 + 202*x^3 - 12*x^4 - 18*x^5 - 22*x^6) / (1 - 18*x^2 - 6*x^3 - 39*x^4 + 2*x^5 + 3*x^6 + 4*x^7). - Colin Barker, Feb 23 2018

Example

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

Crossrefs

Cf. A205520.

Sequence in context: A205520 A236990 A236058 * A017378 A205736 A237850

Adjacent sequences: A205510 A205511 A205512 * A205514 A205515 A205516

Keyword

nonn

Author

R. H. Hardin, Jan 28 2012

Status

approved