a(n) = 64*n^2 - 8.

Terms

a(0) =56a(1) =248a(2) =568a(3) =1016a(4) =1592a(5) =2296a(6) =3128a(7) =4088a(8) =5176a(9) =6392a(10) =7736a(11) =9208a(12) =10808a(13) =12536a(14) =14392a(15) =16376a(16) =18488a(17) =20728a(18) =23096a(19) =25592a(20) =28216a(21) =30968a(22) =33848a(23) =36856a(24) =39992a(25) =43256a(26) =46648a(27) =50168a(28) =53816a(29) =57592