A221938 Number of 2 X n arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, without move-in move-out straight through or left turns.

1, 17, 105, 783, 5622, 40608, 293084, 2115379, 15268366, 110202874, 795416273, 5741108247, 41437835079, 299087573904, 2158736742330, 15581203397143, 112461095655909, 811715097631008, 5858749604657939, 42286939137094085

Offset

1,2

Comments

Row 2 of A221937.

Links

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

Formula

Empirical: a(n) = 3*a(n-1) + 25*a(n-2) + 40*a(n-3) + a(n-4) - 42*a(n-5) - 20*a(n-6) + 10*a(n-7) + 4*a(n-8) -a(n-9).

Empirical g.f.: x*(1 + 14*x + 29*x^2 + 3*x^3 - 33*x^4 - 8*x^5 + 19*x^6 + 4*x^7 - x^8) / (1 - 3*x - 25*x^2 - 40*x^3 - x^4 + 42*x^5 + 20*x^6 - 10*x^7 - 4*x^8 + x^9). - Colin Barker, Aug 11 2018

Example

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

Crossrefs

Cf. A221937.

Sequence in context: A194131 A194475 A164745 * A121823 A268263 A343706

Adjacent sequences: A221935 A221936 A221937 * A221939 A221940 A221941

Keyword

nonn

Author

R. H. Hardin, Feb 01 2013

Status

approved