T(2n-1,n-1), T given by A027157.

Terms

a(0) =2a(1) =6a(2) =40a(3) =152a(4) =1088a(5) =4416a(6) =32384a(7) =135552a(8) =1006592a(9) =4289536a(10) =32100352a(11) =138407936a(12) =1041203200a(13) =4526702592a(14) =34182430720a(15) =149528084480