First differences of A138477.

Terms

a(0) =0a(1) =1a(2) =1a(3) =1a(4) =3a(5) =9a(6) =15a(7) =25a(8) =55a(9) =121a(10) =231a(11) =441a(12) =903a(13) =1849a(14) =3655a(15) =7225a(16) =14535a(17) =29241a(18) =58311a(19) =116281a(20) =232903a(21) =466489a(22) =932295a(23) =1863225a(24) =3727815a(25) =7458361a(26) =14913991a(27) =29822521a(28) =59650503a(29) =119311929