Fourth column of triangle A067323.

Terms

a(0) =5a(1) =19a(2) =66a(3) =227a(4) =785a(5) =2739a(6) =9646a(7) =34268a(8) =122706a(9) =442510a(10) =1605956a(11) =5861481a(12) =21502585a(13) =79243395a(14) =293246550a(15) =1089264360a(16) =4059928950a(17) =15179606010a(18) =56917649820a(19) =213982542150a(20) =806429435994