Number of non-attacking placements of 5 rooks on an n X n board.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =120a(5) =4320a(6) =52920a(7) =376320a(8) =1905120a(9) =7620480a(10) =25613280a(11) =75271680a(12) =198764280a(13) =480960480a(14) =1082161080a(15) =2289530880a(16) =4594961280a(17) =8809274880a(18) =16225246080a(19) =28844881920a(20) =49689816120a(21) =83217546720a(22) =135870624120a(23) =216790801920a(24) =338735628000a(25) =519241008000a(26) =782079948000