1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero, one, two or three horizontal and vertical neighbors.
A211086
1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero, one, two or three horizontal and vertical neighbors.
Terms
- a(0) =1a(1) =16a(2) =960a(3) =229824a(4) =219386880a(5) =834532651008
External references
- oeis: A211086