a(n) = 4*(n+1)*(9*n+4).

Terms

a(0) =16a(1) =104a(2) =264a(3) =496a(4) =800a(5) =1176a(6) =1624a(7) =2144a(8) =2736a(9) =3400a(10) =4136a(11) =4944a(12) =5824a(13) =6776a(14) =7800a(15) =8896a(16) =10064a(17) =11304a(18) =12616a(19) =14000a(20) =15456a(21) =16984a(22) =18584a(23) =20256a(24) =22000a(25) =23816a(26) =25704a(27) =27664a(28) =29696a(29) =31800