a(n) = (8*n + 2)^2.

Terms

a(0) =4a(1) =100a(2) =324a(3) =676a(4) =1156a(5) =1764a(6) =2500a(7) =3364a(8) =4356a(9) =5476a(10) =6724a(11) =8100a(12) =9604a(13) =11236a(14) =12996a(15) =14884a(16) =16900a(17) =19044a(18) =21316a(19) =23716a(20) =26244a(21) =28900a(22) =31684a(23) =34596a(24) =37636a(25) =40804a(26) =44100a(27) =47524a(28) =51076a(29) =54756