a(n) = (n + 3)^2 - 8.

Terms

a(0) =1a(1) =8a(2) =17a(3) =28a(4) =41a(5) =56a(6) =73a(7) =92a(8) =113a(9) =136a(10) =161a(11) =188a(12) =217a(13) =248a(14) =281a(15) =316a(16) =353a(17) =392a(18) =433a(19) =476a(20) =521a(21) =568a(22) =617a(23) =668a(24) =721a(25) =776a(26) =833a(27) =892a(28) =953a(29) =1016