A320404 Number of nX3 0..1 arrays with every element unequal to 0, 1, 2, 4 or 5 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.

4, 14, 47, 156, 548, 1970, 7049, 25364, 91307, 328700, 1183518, 4261468, 15344635, 55253618, 198959548, 716424463, 2579743890, 9289300111, 33449490192, 120447025154, 433713239426, 1561742028021, 5623619418043, 20249884464928

Offset

1,1

Comments

Column 3 of A320409.

Links

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

Formula

Empirical: a(n) = 4*a(n-1) +a(n-2) -6*a(n-3) -7*a(n-4) -18*a(n-5) +15*a(n-6) +23*a(n-7) +67*a(n-8) -3*a(n-9) -72*a(n-10) -53*a(n-11) -44*a(n-12) +47*a(n-13) +23*a(n-14) +23*a(n-15) +37*a(n-16) -20*a(n-17) -8*a(n-18) -12*a(n-19) -8*a(n-20) +13*a(n-21) +2*a(n-22) -3*a(n-23) for n>25

Example

Some solutions for n=5
..0..0..1. .0..1..1. .0..1..1. .0..1..0. .0..0..0. .0..0..1. .0..0..0
..0..0..1. .1..0..0. .1..1..1. .0..0..0. .0..1..0. .0..1..1. .1..1..0
..0..0..1. .1..0..0. .1..1..1. .0..0..0. .1..0..1. .1..1..0. .1..0..0
..1..1..1. .1..0..0. .0..1..1. .0..0..0. .1..1..1. .1..1..1. .0..0..1
..1..1..1. .1..0..0. .1..1..1. .0..1..0. .1..1..1. .1..1..1. .0..0..0

Crossrefs

Cf. A320409.

Sequence in context: A273714 A082574 A289780 * A137284 A365987 A228178

Adjacent sequences: A320401 A320402 A320403 * A320405 A320406 A320407

Keyword

nonn

Author

R. H. Hardin, Oct 12 2018

Status

approved