1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero or two horizontal and vertical neighbors.

A211079

1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero or two horizontal and vertical neighbors.

Terms

    a(0) =1a(1) =10a(2) =228a(3) =12627a(4) =1667397a(5) =527301810a(6) =398763964407

External references