(A192380)/2.

Terms

a(0) =0a(1) =1a(2) =2a(3) =10a(4) =30a(5) =115a(6) =388a(7) =1396a(8) =4860a(9) =17205a(10) =60390a(11) =212894a(12) =748858a(13) =2637095a(14) =9281160a(15) =32674280a(16) =115012472a(17) =404871209a(18) =1425187530a(19) =5016903090a(20) =17660176470a(21) =62166525211a(22) =218835115532a(23) =770332126300