a(n) = n^2 - 7.

Terms

a(0) =2a(1) =9a(2) =18a(3) =29a(4) =42a(5) =57a(6) =74a(7) =93a(8) =114a(9) =137a(10) =162a(11) =189a(12) =218a(13) =249a(14) =282a(15) =317a(16) =354a(17) =393a(18) =434a(19) =477a(20) =522a(21) =569a(22) =618a(23) =669a(24) =722a(25) =777a(26) =834a(27) =893a(28) =954a(29) =1017