1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero, one or four horizontal and vertical neighbors.
A211087
1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero, one or four horizontal and vertical neighbors.
Terms
- a(0) =1a(1) =9a(2) =324a(3) =35343a(4) =12487068a(5) =14118092100
External references
- oeis: A211087