a(n) = self-convolution of row n of array T given by A027023.

Terms

a(0) =1a(1) =3a(2) =9a(3) =31a(4) =129a(5) =531a(6) =2129a(7) =8351a(8) =32177a(9) =122211a(10) =458801a(11) =1706015a(12) =6293169a(13) =23057651a(14) =83992313a(15) =304424639a(16) =1098525761a(17) =3948727555a(18) =14145206209a(19) =50515602111a(20) =179904080257a(21) =639103899411