a(n) = (n/(n+1)) * lcm(1,2,...,n+1).

Terms

a(0) =1a(1) =4a(2) =9a(3) =48a(4) =50a(5) =360a(6) =735a(7) =2240a(8) =2268a(9) =25200a(10) =25410a(11) =332640a(12) =334620a(13) =336336a(14) =675675a(15) =11531520a(16) =11571560a(17) =220540320a(18) =221152932a(19) =221707200a(20) =222211080a(21) =5121436320a(22) =5131136010a(23) =25700298624a(24) =25741485000a(25) =77338861600a(26) =77445096300