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

Terms

a(0) =1a(1) =9a(2) =23a(3) =43a(4) =69a(5) =101a(6) =139a(7) =183a(8) =233a(9) =289a(10) =351a(11) =419a(12) =493a(13) =573a(14) =659a(15) =751a(16) =849a(17) =953a(18) =1063a(19) =1179a(20) =1301a(21) =1429a(22) =1563a(23) =1703a(24) =1849a(25) =2001a(26) =2159a(27) =2323a(28) =2493a(29) =2669