Number of n X n matrices with exactly 2 1's in each row and column, other entries 0.
A001499
Number of n X n matrices with exactly 2 1's in each row and column, other entries 0.
Terms
- a(0) =1a(1) =0a(2) =1a(3) =6a(4) =90a(5) =2040a(6) =67950a(7) =3110940a(8) =187530840a(9) =14398171200
External references
- oeis: A001499