A233218 Number of 2 X n 0..5 arrays with no element x(i,j) adjacent to value 5-x(i,j) horizontally or antidiagonally, top left element zero, and 1 appearing before 2 3 and 4, and 2 appearing before 3 in row major order.

3, 23, 376, 7222, 147019, 3054973, 63927526, 1340889772, 28147567369, 591021089923, 12410898114676, 260625046992322, 5473099292927719, 114934898294104873, 2413631556174561826, 50686253523654314872

Offset

1,1

Links

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

Formula

Empirical: a(n) = 29*a(n-1) - 175*a(n-2) + 147*a(n-3) for n>4.

Conjectures from Colin Barker, Oct 10 2018: (Start)

G.f.: x*(3 - 64*x + 234*x^2 - 98*x^3) / ((1 - x)*(1 - 7*x)*(1 - 21*x)).

a(n) = (2205 + 486*7^n + 125*21^n) / 3528 for n>1.

(End)

Example

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

Crossrefs

Row 2 of A233217.

Sequence in context: A068338 A255881 A243195 * A114601 A178315 A210910

Adjacent sequences: A233215 A233216 A233217 * A233219 A233220 A233221

Keyword

nonn

Author

R. H. Hardin, Dec 06 2013

Status

approved