a(n) = n^3 - 3*(n+3)^2.

Terms

a(0) =-27a(1) =-47a(2) =-67a(3) =-81a(4) =-83a(5) =-67a(6) =-27a(7) =43a(8) =149a(9) =297a(10) =493a(11) =743a(12) =1053a(13) =1429a(14) =1877a(15) =2403a(16) =3013a(17) =3713a(18) =4509a(19) =5407a(20) =6413a(21) =7533a(22) =8773a(23) =10139a(24) =11637a(25) =13273a(26) =15053a(27) =16983a(28) =19069a(29) =21317