Central terms of the triangle in A227550.

Terms

a(0) =1a(1) =2a(2) =8a(3) =36a(4) =176a(5) =940a(6) =5568a(7) =37128a(8) =280992a(9) =2410812a(10) =23250080a(11) =249164344a(12) =2934303264a(13) =37617633976a(14) =521009920256