a(n) = n*lcm{1,2,...,n}.

Terms

a(0) =1a(1) =4a(2) =18a(3) =48a(4) =300a(5) =360a(6) =2940a(7) =6720a(8) =22680a(9) =25200a(10) =304920a(11) =332640a(12) =4684680a(13) =5045040a(14) =5405400a(15) =11531520a(16) =208288080a(17) =220540320a(18) =4423058640a(19) =4655851200a(20) =4888643760a(21) =5121436320a(22) =123147264240a(23) =128501493120a(24) =669278610000a(25) =696049754400