A210896 Number of n X n 0..2 symmetric matrices with every element equal to zero or one horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order

1, 2, 20, 400, 16716, 1444348, 258951340, 96266852004, 74214689922928, 118642250445743920, 393305989512539553728, 2703723885515478100466476, 38542035415959856159523945096

Offset

1,2

Links

Table of n, a(n) for n=1..13.

Example

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

Crossrefs

Sequence in context: A009236 A078698 A090728 * A090309 A002116 A058346

Adjacent sequences: A210893 A210894 A210895 * A210897 A210898 A210899

Keyword

nonn

Author

R. H. Hardin Mar 29 2012

Status

approved