a(n) = (1/4)*A073388(n+1).

Terms

a(0) =1a(1) =4a(2) =14a(3) =47a(4) =152a(5) =480a(6) =1488a(7) =4548a(8) =13744a(9) =41152a(10) =122272a(11) =360944a(12) =1059584a(13) =3095552a(14) =9005568a(15) =26101824a(16) =75404544a(17) =217191424a(18) =623928832a(19) =1788071680a(20) =5113137152a(21) =14592352256a(22) =41569120256a(23) =118219097088a(24) =335685021696a(25) =951817715712