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

1,1

Comments

Column 4 of A224665

Links

Table of n, a(n) for n=1..12.

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..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

Crossrefs

Sequence in context: A196532 A002745 A182959 * A357786 A020046 A319731

Adjacent sequences: A224658 A224659 A224660 * A224662 A224663 A224664

Keyword

nonn

Author

R. H. Hardin Apr 14 2013

Status

approved