1/16 the number of (n+1) X 7 0..3 arrays with all 2 X 2 subblocks having the same four values.

Terms

a(0) =325a(1) =337a(2) =358a(3) =400a(4) =478a(5) =634a(6) =934a(7) =1534a(8) =2710a(9) =5062a(10) =9718a(11) =19030a(12) =37558a(13) =74614a(14) =148534a(15) =296374a(16) =591670a(17) =1182262a(18) =2362678a(19) =4723510a(20) =9443638a(21) =18883894a(22) =37761334a(23) =75516214a(24) =151019830a(25) =302027062a(26) =604029238a(27) =1208033590a(28) =2416017718a(29) =4831985974