Third column of triangle A067323.

Terms

a(0) =2a(1) =7a(2) =23a(3) =76a(4) =255a(5) =869a(6) =3003a(7) =10504a(8) =37128a(9) =132430a(10) =476102a(11) =1723528a(12) =6277505a(13) =22988385a(14) =84592275a(15) =312636240a(16) =1159979700a(17) =4319218530a(18) =16134883410a(19) =60452176200a(20) =227110782990a(21) =855361970034