a(n) = A131120(n+1)/n.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =2a(6) =12a(7) =12a(8) =12a(9) =12a(10) =120a(11) =120a(12) =1440a(13) =1440a(14) =10080a(15) =30240a(16) =60480a(17) =60480a(18) =120960a(19) =120960a(20) =2419200a(21) =7257600a(22) =79833600a(23) =79833600a(24) =479001600a(25) =479001600a(26) =12454041600a(27) =12454041600a(28) =174356582400a(29) =174356582400