1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero or one horizontal and vertical neighbors.
A211077
1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero or one horizontal and vertical neighbors.
Terms
- a(0) =1a(1) =9a(2) =297a(3) =30213a(4) =9904329a(5) =10357083063
External references
- oeis: A211077