a(n) = n * binomial(2*n, n-1).

Terms

a(0) =0a(1) =1a(2) =8a(3) =45a(4) =224a(5) =1050a(6) =4752a(7) =21021a(8) =91520a(9) =393822a(10) =1679600a(11) =7113106a(12) =29953728a(13) =125550100a(14) =524190240a(15) =2181340125a(16) =9051563520a(17) =37467344310a(18) =154754938800a(19) =637982011590