a(n) = n!*(floor(n/30))!/((floor(n/2))!*(floor(n/3))!*(floor(n/5))!).

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =12a(5) =60a(6) =60a(7) =420a(8) =840a(9) =2520a(10) =2520a(11) =27720a(12) =13860a(13) =180180a(14) =360360a(15) =360360a(16) =720720a(17) =12252240a(18) =4084080a(19) =77597520a(20) =38798760a(21) =116396280a(22) =232792560a(23) =5354228880a(24) =1338557220a(25) =6692786100a(26) =13385572200a(27) =40156716600a(28) =80313433200a(30) =77636318760