A224661 Number of n X n 0..4 matrices with each 2X2 subblock idempotent.

5, 20, 98, 180, 412, 806, 1606, 3070, 5808, 10798, 19866, 36184

Offset: 1

Author

R. H. Hardin Apr 14 2013

Keywords

• nonn

Comments

Column 4 of A224665

Examples

			Some solutions for n=3
..1..0..2....1..0..3....0..0..0....0..0..0....1..0..0....1..1..0....0..0..0
..1..0..1....1..0..1....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0
..4..0..1....2..0..1....2..1..1....0..0..0....0..0..1....0..0..1....4..1..1
		

Formula

Empirical: a(n) = 6*a(n-1) -12*a(n-2) +5*a(n-3) +12*a(n-4) -12*a(n-5) -3*a(n-6) +6*a(n-7) -a(n-9) for n>10