A205919 Number of (n+1) X 2 0..3 arrays with the number of clockwise edge increases in every 2 X 2 subblock equal to one, and every 2 X 2 determinant nonzero.

76, 389, 1828, 9144, 43572, 215294, 1035724, 5082472, 24576282, 120140890, 582580746, 2841986300, 13802576730, 67255368928, 326915006288, 1591943059154, 7741739157470, 37686051760598, 183317203390912, 892200827543090

Offset

1,1

Comments

Column 1 of A205926.

Links

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

Formula

Empirical: a(n) = a(n-1) + 18*a(n-2) + 3*a(n-3) - 2*a(n-4) + 26*a(n-5) + 28*a(n-6) + 8*a(n-7).

Empirical g.f.: x*(76 + 313*x + 71*x^2 + 86*x^3 + 509*x^4 + 448*x^5 + 116*x^6) / (1 - x - 18*x^2 - 3*x^3 + 2*x^4 - 26*x^5 - 28*x^6 - 8*x^7). - Colin Barker, Jun 13 2018

Example

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

Crossrefs

Cf. A205926.

Sequence in context: A234184 A234177 A205926 * A238918 A234786 A234779

Adjacent sequences: A205916 A205917 A205918 * A205920 A205921 A205922

Keyword

nonn

Author

R. H. Hardin, Feb 01 2012

Status

approved