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

A211037

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

Terms

    a(0) =1a(1) =5a(2) =34a(3) =398a(4) =6988a(5) =197328a(6) =8645790a(7) =598407040a(8) =64812874208

External references