1/3 the number of n X n 0..2 symmetric matrices with every element equal to zero, one or three horizontal and vertical neighbors.
A211040
1/3 the number of n X n 0..2 symmetric matrices with every element equal to zero, one or three horizontal and vertical neighbors.
Terms
- a(0) =1a(1) =4a(2) =40a(3) =928a(4) =45128a(5) =4945168a(6) =1207742160a(7) =655725571768
External references
- oeis: A211040