a(n) = (n-1)*(2*n-1)*(3*n-1).

Terms

a(0) =-1a(1) =0a(2) =15a(3) =80a(4) =231a(5) =504a(6) =935a(7) =1560a(8) =2415a(9) =3536a(10) =4959a(11) =6720a(12) =8855a(13) =11400a(14) =14391a(15) =17864a(16) =21855a(17) =26400a(18) =31535a(19) =37296a(20) =43719a(21) =50840a(22) =58695a(23) =67320a(24) =76751a(25) =87024a(26) =98175a(27) =110240a(28) =123255a(29) =137256