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

1,1

Comments

Column 3 of A224665.

Links

Table of n, a(n) for n=1..25.

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.

Example

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

Crossrefs

Sequence in context: A161797 A124533 A227034 * A330610 A327541 A158784

Adjacent sequences: A224657 A224658 A224659 * A224661 A224662 A224663

Keyword

nonn,more

Author

R. H. Hardin, Apr 14 2013

Status

approved