A221610 Number of 2 X n arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor, without move-in move-out left turns.

0, 2, 10, 53, 269, 1378, 7057, 36152, 185192, 948664, 4859596, 24893585, 127518875, 653222944, 3346172776, 17140965623, 87805597652, 449789301892, 2304071965189, 11802743188937, 60460241206049, 309711116141929, 1586513277940591

Offset

1,2

Comments

Row 2 of A221609.

Links

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

Formula

Empirical: a(n) = 7*a(n-1) - 9*a(n-2) - 5*a(n-3) + 10*a(n-4) - 3*a(n-5) for n>7.

Empirical g.f.: x^2*(1 - x - x^2)*(2 - 2*x + x^2 - 3*x^3) / (1 - 7*x + 9*x^2 + 5*x^3 - 10*x^4 + 3*x^5). - Colin Barker, Aug 09 2018

Example

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

Crossrefs

Cf. A221609.

Sequence in context: A057415 A037724 A037619 * A247102 A370390 A009320

Adjacent sequences: A221607 A221608 A221609 * A221611 A221612 A221613

Keyword

nonn

Author

R. H. Hardin, Jan 20 2013

Status

approved