a(n) = 3*n^3.

Terms

a(0) =0a(1) =3a(2) =24a(3) =81a(4) =192a(5) =375a(6) =648a(7) =1029a(8) =1536a(9) =2187a(10) =3000a(11) =3993a(12) =5184a(13) =6591a(14) =8232a(15) =10125a(16) =12288a(17) =14739a(18) =17496a(19) =20577a(20) =24000a(21) =27783a(22) =31944a(23) =36501a(24) =41472a(25) =46875a(26) =52728a(27) =59049a(28) =65856a(29) =73167