a(n) = 2*n^2 + 10*n + 3.

Terms

a(0) =3a(1) =15a(2) =31a(3) =51a(4) =75a(5) =103a(6) =135a(7) =171a(8) =211a(9) =255a(10) =303a(11) =355a(12) =411a(13) =471a(14) =535a(15) =603a(16) =675a(17) =751a(18) =831a(19) =915a(20) =1003a(21) =1095a(22) =1191a(23) =1291a(24) =1395a(25) =1503a(26) =1615a(27) =1731a(28) =1851a(29) =1975