The number of tilings of an 8 X n floor with 1 X 4 tetrominoes.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =7a(5) =15a(6) =25a(7) =37a(8) =100a(9) =229a(10) =454a(11) =811a(12) =1732a(13) =3777a(14) =7858a(15) =15339a(16) =31273a(17) =65536a(18) =136600a(19) =276535a(20) =562728a(21) =1159942a(22) =2400783a(23) =4918159a(24) =10052140a(25) =20627526a(26) =42480474a(27) =87254743a(28) =178855138a(29) =366854368