A224661 - OEIS

%I #4 Dec 18 2015 18:18:35

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

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

%C Column 4 of A224665

%F 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

%e Some solutions for n=3

%e ..1..0..2....1..0..3....0..0..0....0..0..0....1..0..0....1..1..0....0..0..0

%e ..1..0..1....1..0..1....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0

%e ..4..0..1....2..0..1....2..1..1....0..0..0....0..0..1....0..0..1....4..1..1

%K nonn

%O 1,1

%A _R. H. Hardin_ Apr 14 2013