A268794 Number of nX4 0..2 arrays with some element plus some horizontally, vertically or antidiagonally adjacent neighbor totalling two exactly once.

36, 234, 950, 4800, 23994, 117062, 561116, 2652936, 12405748, 57490444, 264428454, 1208522850, 5493284922, 24851601802, 111963916212, 502590509990, 2248738675490, 10032298715910, 44640056867750, 198161794087570

Offset: 1

Author

R. H. Hardin, Feb 13 2016

Keywords

• nonn

Comments

Column 4 of A268798.

Examples

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

Links

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

Crossrefs

Cf. A268798.

Formula

Empirical: a(n) = 2*a(n-1) +19*a(n-2) +10*a(n-3) -122*a(n-4) -320*a(n-5) -295*a(n-6) +8*a(n-7) +176*a(n-8) +20*a(n-9) -98*a(n-10) -6*a(n-11) +43*a(n-12) -6*a(n-13) -11*a(n-14) +6*a(n-15) -a(n-16) for n>19