a(n) = 3*n^2 + 3*n - 5.

Terms

a(0) =1a(1) =13a(2) =31a(3) =55a(4) =85a(5) =121a(6) =163a(7) =211a(8) =265a(9) =325a(10) =391a(11) =463a(12) =541a(13) =625a(14) =715a(15) =811a(16) =913a(17) =1021a(18) =1135a(19) =1255a(20) =1381a(21) =1513a(22) =1651a(23) =1795a(24) =1945a(25) =2101a(26) =2263a(27) =2431a(28) =2605a(29) =2785