a(n) = 2*a(n-1) + 2*a(n-2) - 4*a(n-3), a(1) = 0, a(2) = 0, a(3) = 8.

Terms

a(0) =0a(1) =0a(2) =8a(3) =16a(4) =48a(5) =96a(6) =224a(7) =448a(8) =960a(9) =1920a(10) =3968a(11) =7936a(12) =16128a(13) =32256a(14) =65024a(15) =130048a(16) =261120a(17) =522240a(18) =1046528a(19) =2093056a(20) =4190208a(21) =8380416a(22) =16769024a(23) =33538048a(24) =67092480a(25) =134184960a(26) =268402688a(27) =536805376a(28) =1073676288a(29) =2147352576