a(n) = 58*n^2 - 1.

Terms

a(0) =57a(1) =231a(2) =521a(3) =927a(4) =1449a(5) =2087a(6) =2841a(7) =3711a(8) =4697a(9) =5799a(10) =7017a(11) =8351a(12) =9801a(13) =11367a(14) =13049a(15) =14847a(16) =16761a(17) =18791a(18) =20937a(19) =23199a(20) =25577a(21) =28071a(22) =30681a(23) =33407a(24) =36249a(25) =39207a(26) =42281a(27) =45471a(28) =48777a(29) =52199