Number of fault-free tilings of a 3 X n rectangle with squares and dominoes.

Terms

a(0) =0a(1) =0a(2) =2a(3) =2a(4) =10a(5) =16a(6) =52a(7) =104a(8) =286a(9) =634a(10) =1622a(11) =3768a(12) =9336a(13) =22152a(14) =54106a(15) =129610a(16) =314546a(17) =756728a(18) =1831196a(19) =4413952a(20) =10667462a(21) =25735346a(22) =62160046a(23) =150020016a(24) =362257392a(25) =874442064a(26) =2111291570a(27) =5096782418a(28) =12305249242a(29) =29706645280