Number of ways to place 3n rooks on an n X n board, with 3 rooks in each row and each column, multiple rooks in a cell allowed, and exactly 3 rooks below the main diagonal.
A260727
Number of ways to place 3n rooks on an n X n board, with 3 rooks in each row and each column, multiple rooks in a cell allowed, and exactly 3 rooks below the main diagonal.
Terms
- a(0) =1a(1) =23a(2) =325a(3) =3368a(4) =28819a(5) =218788a(6) =1539399a(7) =10314315a(8) =66953292a(9) =425761614a(10) =2671506918a(11) =16618186770a(12) =102796975770a(13) =633596982417
External references
- oeis: A260727