a(n) = 76*n^2 - 1.

Terms

a(0) =75a(1) =303a(2) =683a(3) =1215a(4) =1899a(5) =2735a(6) =3723a(7) =4863a(8) =6155a(9) =7599a(10) =9195a(11) =10943a(12) =12843a(13) =14895a(14) =17099a(15) =19455a(16) =21963a(17) =24623a(18) =27435a(19) =30399a(20) =33515a(21) =36783a(22) =40203a(23) =43775a(24) =47499a(25) =51375a(26) =55403a(27) =59583a(28) =63915a(29) =68399