Bisection of Motzkin numbers A001006.

Terms

a(0) =1a(1) =4a(2) =21a(3) =127a(4) =835a(5) =5798a(6) =41835a(7) =310572a(8) =2356779a(9) =18199284a(10) =142547559a(11) =1129760415a(12) =9043402501a(13) =73007772802a(14) =593742784829