A210928 Number of n X n 0..3 symmetric matrices with every element equal to zero or one horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order.

1, 2, 55, 5892, 2081181, 2353015360, 8533282805517, 99227545384370981, 3699909251614783425693, 442375363534050667939662012, 169602369911112134429648742314656

Offset

1,2

Links

Table of n, a(n) for n=1..11.

Example

Some solutions for n=4
..0..1..2..0....0..1..3..0....0..1..1..2....0..1..2..1....0..1..3..3
..1..2..1..3....1..2..0..2....1..2..3..1....1..0..3..3....1..2..0..0
..2..1..2..3....3..0..1..2....1..3..1..2....2..3..2..1....3..0..3..2
..0..3..3..2....0..2..2..0....2..1..2..3....1..3..1..0....3..0..2..0

Crossrefs

Sequence in context: A186886 A024029 A134501 * A210932 A278842 A307025

Adjacent sequences: A210925 A210926 A210927 * A210929 A210930 A210931

Keyword

nonn

Author

R. H. Hardin, Mar 29 2012

Status

approved