Number of tilings of a 27 X n rectangle using 3n nonominoes of shape I.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =1a(7) =1a(8) =1a(9) =76a(10) =195a(11) =364a(12) =589a(13) =876a(14) =1231a(15) =1660a(16) =2169a(17) =2764a(18) =21232a(19) =57379a(20) =123291a(21) =235860a(22) =417784a(23) =698657a(24) =1116149a(25) =1717276a(26) =2559760a(27) =7386240a(28) =18797731a(29) =42769684