A183359 One quarter the number of nX7 1..4 arrays with no two neighbors of any element equal to each other.

972, 36864, 34992, 63504, 137088, 331776, 829440, 1806336, 3852288, 8294400, 18137088, 40144896, 88897536, 196448256, 433465344, 955551744, 2106667008, 4645785600, 10246588416, 22600912896, 49849804800, 109947949056

Offset: 1

Author

R. H. Hardin Jan 04 2011

Keywords

• nonn

Comments

Column 7 of A183362

Examples

			Some solutions for 5X7 with a(1,1)=1
..1..1..2..3..1..2..2....1..1..3..4..2..1..1....1..2..3..4..1..1..3
..2..4..4..3..1..4..4....2..4..3..1..2..4..3....3..2..1..4..3..2..2
..2..3..1..2..2..3..3....3..4..2..1..3..4..2....3..4..1..2..3..4..4
..4..3..1..4..4..1..1....3..1..2..4..3..1..2....2..4..3..2..1..1..3
..4..2..2..3..3..2..2....2..1..3..4..2..1..4....1..1..3..4..4..2..2
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..58

Formula

Empirical: a(n)=2*a(n-1)+a(n-3)-2*a(n-4)+4*a(n-5)+a(n-6)-a(n-9) for n>14