a(1)=1, a(n) = LCM of the integers, from 1 to n/2, which are coprime to n.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =1a(6) =6a(7) =3a(8) =4a(9) =3a(10) =60a(11) =5a(12) =60a(13) =15a(14) =28a(15) =105a(16) =840a(17) =35a(18) =2520a(19) =63a(20) =40a(21) =315a(22) =27720a(23) =385a(24) =5544a(25) =3465a(26) =40040a(27) =6435a(28) =360360a(29) =1001