1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero, one or three horizontal and vertical neighbors.
A211082
1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero, one or three horizontal and vertical neighbors.
Terms
- a(0) =1a(1) =9a(2) =297a(3) =31671a(4) =11073510a(5) =12788362323
External references
- oeis: A211082