A207026 Number of 3Xn 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 0 1 and 1 0 1 vertically.

6, 36, 90, 252, 624, 1350, 3025, 6256, 12788, 25792, 50630, 99012, 190920, 365041, 694038, 1309524, 2460150, 4599952, 8565768, 15899422, 29415965, 54278252, 99908040, 183482116, 336298170, 615243752, 1123669472, 2049072321, 3731220822

Offset: 1

Author

R. H. Hardin Feb 14 2012

Keywords

• nonn

Comments

Row 3 of A207024

Examples

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

Links

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

Formula

Empirical: a(n) = 3*a(n-1) +a(n-2) -5*a(n-3) -10*a(n-4) +12*a(n-5) +11*a(n-6) +a(n-7) -15*a(n-8) +a(n-9) -7*a(n-10) +3*a(n-11) +3*a(n-12) +9*a(n-13) -4*a(n-14) -2*a(n-16) -a(n-18) +a(n-19)