a(n) is the least common multiple of numbers in {1,2,3,...,n-1} which do not divide n.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =12a(5) =20a(6) =60a(7) =210a(8) =840a(9) =504a(10) =2520a(11) =27720a(12) =27720a(13) =51480a(14) =360360a(15) =180180a(16) =720720a(17) =4084080a(18) =12252240a(19) =232792560a(20) =232792560a(21) =21162960a(22) =232792560a(23) =5354228880a(24) =5354228880a(25) =2059318800a(26) =26771144400a(27) =80313433200a(28) =80313433200