1/3 the number of n X n 0..2 symmetric matrices with every element equal to zero, one or four horizontal and vertical neighbors.
A211045
1/3 the number of n X n 0..2 symmetric matrices with every element equal to zero, one or four horizontal and vertical neighbors.
Terms
- a(0) =1a(1) =4a(2) =48a(3) =1104a(4) =54408a(5) =5624336a(6) =1223018480a(7) =559805180336
External references
- oeis: A211045