a(n) = 16*n^2 + 4.

Terms

a(0) =20a(1) =68a(2) =148a(3) =260a(4) =404a(5) =580a(6) =788a(7) =1028a(8) =1300a(9) =1604a(10) =1940a(11) =2308a(12) =2708a(13) =3140a(14) =3604a(15) =4100a(16) =4628a(17) =5188a(18) =5780a(19) =6404a(20) =7060a(21) =7748a(22) =8468a(23) =9220a(24) =10004a(25) =10820a(26) =11668a(27) =12548a(28) =13460a(29) =14404