1/4 the number of n X n 0..3 symmetric matrices with every element equal to one, two or three horizontal and vertical neighbors.
A211085
1/4 the number of n X n 0..3 symmetric matrices with every element equal to one, two or three horizontal and vertical neighbors.
Terms
- a(0) =0a(1) =1a(2) =12a(3) =504a(4) =54552a(5) =18314238a(6) =18001425828
External references
- oeis: A211085