

A224660


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


0



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
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OFFSET

1,1


COMMENTS

Column 3 of A224665.


LINKS

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


FORMULA

Empirical: a(n) = 6*a(n1) 12*a(n2) +5*a(n3) +12*a(n4) 12*a(n5) 3*a(n6) +6*a(n7) a(n9) 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



