First differences of [0, A047970].

Terms

a(0) =1a(1) =1a(2) =3a(3) =9a(4) =29a(5) =101a(6) =379a(7) =1525a(8) =6549a(9) =29889a(10) =144419a(11) =736241a(12) =3947725a(13) =22201549a(14) =130624587a(15) =802180701a(16) =5131183301a(17) =34121977865a(18) =235486915507