Number of tilings of a 5 X 2n rectangle using 2n pentominoes of shape P.

Terms

a(0) =1a(1) =2a(2) =6a(3) =20a(4) =62a(5) =194a(6) =612a(7) =1922a(8) =6038a(9) =18980a(10) =59646a(11) =187442a(12) =589076a(13) =1851266a(14) =5817894a(15) =18283700a(16) =57459518a(17) =180575906a(18) =567489348a(19) =1783428098a(20) =5604714422a(21) =17613731780a(22) =55354032894a(23) =173959101458a(24) =546694927604