a(n) = 36*n^2 - 17*n + 2.

Terms

a(0) =21a(1) =112a(2) =275a(3) =510a(4) =817a(5) =1196a(6) =1647a(7) =2170a(8) =2765a(9) =3432a(10) =4171a(11) =4982a(12) =5865a(13) =6820a(14) =7847a(15) =8946a(16) =10117a(17) =11360a(18) =12675a(19) =14062a(20) =15521a(21) =17052a(22) =18655a(23) =20330a(24) =22077a(25) =23896a(26) =25787a(27) =27750a(28) =29785a(29) =31892