1/3 the number of (2n) X (2n) 0..2 symmetric matrices with every element equal to two horizontal and vertical neighbors.

A211036

1/3 the number of (2n) X (2n) 0..2 symmetric matrices with every element equal to two horizontal and vertical neighbors.

Terms

    a(0) =1a(1) =6a(2) =70a(3) =1584a(4) =69094a(5) =5804980a(6) =937523156a(7) =290938653352

External references