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

Terms

a(0) =0a(1) =-1a(2) =4a(3) =27a(4) =80a(5) =175a(6) =324a(7) =539a(8) =832a(9) =1215a(10) =1700a(11) =2299a(12) =3024a(13) =3887a(14) =4900a(15) =6075a(16) =7424a(17) =8959a(18) =10692a(19) =12635a(20) =14800a(21) =17199a(22) =19844a(23) =22747a(24) =25920a(25) =29375a(26) =33124a(27) =37179a(28) =41552a(29) =46255