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

A211092

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

Terms

    a(0) =0a(1) =1a(2) =1a(3) =19a(4) =136a(5) =3496a(6) =100204a(7) =6012109a(8) =537556135a(9) =86449986124

External references