a(n) = (6*n + 1)*(12*n + 1)*(18*n + 1).

Terms

a(0) =1a(1) =1729a(2) =12025a(3) =38665a(4) =89425a(5) =172081a(6) =294409a(7) =464185a(8) =689185a(9) =977185a(10) =1335961a(11) =1773289a(12) =2296945a(13) =2914705a(14) =3634345a(15) =4463641a(16) =5410369a(17) =6482305a(18) =7687225a(19) =9032905a(20) =10527121a(21) =12177649a(22) =13992265a(23) =15978745a(24) =18144865a(25) =20498401a(26) =23047129a(27) =25798825a(28) =28761265a(29) =31942225