A213690 Half the number of (n+1)X(n+1) symmetric 0..1 arrays with no 2X2 subblock summing to 2.

3, 13, 70, 529, 5148, 68798, 1220409, 29377751, 949700962, 41536397680, 2450653487731, 195553849371916, 21091722699002539, 3077853629320011499, 607688763160596614184, 162407853243770174812161

Offset: 1

Author

R. H. Hardin Jun 18 2012

Keywords

• nonn

Comments

Column 1 of A213697

Examples

			Some solutions for n=4
..1..0..0..0..0....0..0..1..0..1....0..1..0..1..0....1..1..0..1..1
..0..0..1..0..1....0..1..1..1..1....1..1..1..1..1....1..1..1..1..1
..0..1..1..1..1....1..1..0..1..0....0..1..1..1..1....0..1..1..1..0
..0..0..1..1..1....0..1..1..1..1....1..1..1..0..1....1..1..1..0..0
..0..1..1..1..1....1..1..0..1..0....0..1..1..1..1....1..1..0..0..0
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..18