A sequence related to Catalan numbers A000108.

Terms

a(0) =1a(1) =2a(2) =4a(3) =16a(4) =80a(5) =448a(6) =2688a(7) =16896a(8) =109824a(9) =732160a(10) =4978688a(11) =34398208a(12) =240787456a(13) =1704034304a(14) =12171673600a(15) =87636049920a(16) =635361361920