a(n) = 3*n^2 + n - 1.

Terms

a(0) =3a(1) =13a(2) =29a(3) =51a(4) =79a(5) =113a(6) =153a(7) =199a(8) =251a(9) =309a(10) =373a(11) =443a(12) =519a(13) =601a(14) =689a(15) =783a(16) =883a(17) =989a(18) =1101a(19) =1219a(20) =1343a(21) =1473a(22) =1609a(23) =1751a(24) =1899a(25) =2053a(26) =2213a(27) =2379a(28) =2551a(29) =2729