a(0)=1, a(1)=2, a(n) = a(n-1)*9/2 - Catalan(n-1) where Catalan(n) = binomial(2n,n)/(n+1) = A000108(n).

A067336

a(0)=1, a(1)=2, a(n) = a(n-1)*9/2 - Catalan(n-1) where Catalan(n) = binomial(2n,n)/(n+1) = A000108(n).

Terms

    a(0) =1a(1) =2a(2) =8a(3) =34a(4) =148a(5) =652a(6) =2892a(7) =12882a(8) =57540a(9) =257500a(10) =1153888a(11) =5175700a(12) =23231864a(13) =104335376a(14) =468766292a(15) =2106773874a(16) =9470787588a(17) =42583186476a(18) =191494694352a(19) =861248485884

External references