Leftmost column sequence of triangle A073153.

Terms

a(0) =1a(1) =1a(2) =4a(3) =14a(4) =56a(5) =237a(6) =1046a(7) =4762a(8) =22198a(9) =105430a(10) =508384a(11) =2482297a(12) =12248416a(13) =60980875a(14) =305955356a(15) =1545397464a(16) =7852100294a(17) =40105277640a(18) =205798130604