A221421 Number of 3Xn arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, with every occupancy equal to zero or two

0, 8, 0, 226, 0, 6798, 0, 198823, 0, 5789134, 0, 168353683, 0, 4894400220, 0, 142279944512, 0, 4135993312056, 0, 120230312311224, 0, 3495003621811704, 0, 101597065323229956, 0, 2953348289319127152, 0, 85851554285154067136, 0

Offset

1,2

Comments

Row 3 of A221419

Links

R. H. Hardin, Table of n, a(n) for n = 1..202

Formula

Empirical: a(n) = 36*a(n-2) -200*a(n-4) -40*a(n-6) -84*a(n-8) +80*a(n-10) -20*a(n-12) +80*a(n-14) for n>20

Example

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

Crossrefs

Sequence in context: A121770 A221379 A013376 * A371990 A013456 A180738

Adjacent sequences: A221418 A221419 A221420 * A221422 A221423 A221424

Keyword

nonn

Author

R. H. Hardin Jan 15 2013

Status

approved