1/4 the number of n X n 0..3 symmetric matrices with every element equal to one, two or four horizontal and vertical neighbors.
A211089
1/4 the number of n X n 0..3 symmetric matrices with every element equal to one, two or four horizontal and vertical neighbors.
Terms
- a(0) =0a(1) =1a(2) =6a(3) =348a(4) =28140a(5) =8126604a(6) =5661794106
External references
- oeis: A211089