A224660 Number of n X n 0..3 matrices with each 2 X 2 subblock idempotent.

4, 16, 72, 142, 332, 668, 1356, 2634, 5046, 9480, 17594, 32286, 58730, 106028, 190204, 339322, 602416, 1064888, 1875104, 3290166, 5754586, 10035236, 17452462, 30275242, 52395822

Offset: 1

Author

R. H. Hardin, Apr 14 2013

Keywords

• nonn
• more

Comments

Column 3 of A224665.

Examples

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