Number of tilings of a 4 X n rectangle using L tetrominoes and 2 X 2 tiles.

Terms

a(0) =1a(1) =0a(2) =3a(3) =6a(4) =19a(5) =48a(6) =141a(7) =378a(8) =1063a(9) =2920a(10) =8115a(11) =22418a(12) =62123a(13) =171876a(14) =475919a(15) =1317250a(16) =3646681a(17) =10094356a(18) =27943739a(19) =77353070a(20) =214129845a(21) =592752572a(22) =1640859689a(23) =4542223926a(24) =12573787053a(25) =34806745800a(26) =96352029241a(27) =266721635838a(28) =738338745535