Number of tilings of a 18 X n rectangle using 2n 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) =12a(10) =25a(11) =40a(12) =57a(13) =76a(14) =97a(15) =120a(16) =145a(17) =172a(18) =400a(19) =809a(20) =1449a(21) =2376a(22) =3652a(23) =5345a(24) =7529a(25) =10284a(26) =13696a(27) =21232a(28) =35417a(29) =60028