Fourth column of triangle A028364.

Terms

a(0) =14a(1) =28a(2) =76a(3) =227a(4) =715a(5) =2333a(6) =7810a(7) =26663a(8) =92456a(9) =324700a(10) =1152464a(11) =4127294a(12) =14895145a(13) =54115895a(14) =197764350a(15) =726473055a(16) =2680979820a(17) =9934884960a(18) =36953107320a(19) =137913387450a(20) =516295313430