Number of n X n symmetric 0..3 arrays with each element equal to at least one horizontal or vertical neighbor and any new values 0..3 introduced in lower triangular row major order.
A192640
Number of n X n symmetric 0..3 arrays with each element equal to at least one horizontal or vertical neighbor and any new values 0..3 introduced in lower triangular row major order.
Terms
- a(0) =0a(1) =1a(2) =5a(3) =137a(4) =15055a(5) =5986313a(6) =7174532375
External references
- oeis: A192640