A210926 Number of n X n 0..3 symmetric matrices with every element equal to one, two or three horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order.
0, 1, 4, 95, 9220, 3055073, 3000338892, 8812917082915, 76878364475257062, 1995945343880703817038, 154116672749530867319434810
Offset: 1
Keywords
Examples
Some solutions for n=4 ..0..0..1..0....0..0..1..1....0..0..0..1....0..0..0..0....0..0..1..1 ..0..0..1..0....0..0..1..1....0..1..1..1....0..1..1..0....0..0..1..0 ..1..1..2..2....1..1..1..0....0..1..1..0....0..1..1..0....1..1..1..0 ..0..0..2..2....1..1..0..0....1..1..0..0....0..0..0..0....1..0..0..0