A281690 Number of nX3 0..2 arrays with no element equal to more than one of its horizontal, diagonal or antidiagonal neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.

0, 6, 847, 19326, 293814, 3714629, 42265965, 449985840, 4571830360, 44873281735, 428836383879, 4011945910730, 36886705974618, 334269681986457, 2992281836910513, 26505969364372244, 232662102182106796

Offset

1,2

Comments

Column 3 of A281693.

Links

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

Formula

Empirical: a(n) = 21*a(n-1) -117*a(n-2) -155*a(n-3) +2070*a(n-4) +2406*a(n-5) -15836*a(n-6) -33948*a(n-7) +35640*a(n-8) +184600*a(n-9) +158208*a(n-10) -213408*a(n-11) -613504*a(n-12) -616320*a(n-13) -307200*a(n-14) -64000*a(n-15) for n>20

Example

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

Crossrefs

Cf. A281693.

Sequence in context: A249126 A337162 A378386 * A201141 A078927 A064430

Adjacent sequences: A281687 A281688 A281689 * A281691 A281692 A281693

Keyword

nonn

Author

R. H. Hardin, Jan 27 2017

Status

approved