Number of tilings of a 4 X n rectangle using straight (3 X 1) trominoes and 2 X 2 tiles.

Terms

a(0) =1a(1) =0a(2) =1a(3) =3a(4) =3a(5) =8a(6) =21a(7) =31a(8) =70a(9) =165a(10) =286a(11) =615a(12) =1351a(13) =2548a(14) =5353a(15) =11343a(16) =22320a(17) =46349a(18) =96516a(19) =193944a(20) =400313a(21) =826747a(22) =1678540a(23) =3453642a(24) =7105102a(25) =14498569a(26) =29781633a(27) =61158957a(28) =125108639a(29) =256763850