Triangle read by rows: T(n,k) is the number of ways to place 2*n rooks on a (n+k) X (2*n-k) board so that there is at least one rook in every column and row and so that each rook is defended by another.
A382776
Triangle read by rows: T(n,k) is the number of ways to place 2*n rooks on a (n+k) X (2*n-k) board so that there is at least one rook in every column and row and so that each rook is defended by another.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =6a(4) =9a(5) =6a(6) =90a(7) =180a(8) =180a(9) =90a(10) =2520a(11) =6300a(12) =8100a(13) =6300a(14) =2520a(15) =113400a(16) =340200a(17) =529200a(18) =529200a(19) =340200a(20) =113400a(21) =7484400a(22) =26195400a(23) =47628000a(24) =57153600a(25) =47628000a(26) =26195400a(27) =7484400a(28) =681080400a(29) =2724321600
External references
- oeis: A382776