Number of tilings of a 4 X n rectangle using L and T tetrominoes.

Terms

a(0) =1a(1) =0a(2) =2a(3) =4a(4) =12a(5) =16a(6) =76a(7) =128a(8) =386a(9) =832a(10) =2368a(11) =5024a(12) =13946a(13) =31680a(14) =82632a(15) =193696a(16) =498174a(17) =1182464a(18) =2993384a(19) =7213648a(20) =18061074a(21) =43832960a(22) =109163384a(23) =266217472a(24) =660116398a(25) =1615451648a(26) =3995295112a(27) =9796774896a(28) =24189684402a(29) =59396496000