a(n) = A026907(2*n, n).

Terms

a(0) =1a(1) =44a(2) =198a(3) =758a(4) =2824a(5) =10530a(6) =39516a(7) =149274a(8) =567120a(9) =2164898a(10) =8297206a(11) =31907214a(12) =123053938a(13) =475753142a(14) =1843357752a(15) =7155936162a(16) =27826486272a(17) =108369397602a(18) =422614721742