Successive differences of A000990.

Terms

a(0) =1a(1) =0a(2) =2a(3) =2a(4) =5a(5) =6a(6) =13a(7) =16a(8) =30a(9) =40a(10) =66a(11) =90a(12) =142a(13) =192a(14) =290a(15) =396a(16) =575a(17) =782a(18) =1112a(19) =1500a(20) =2092a(21) =2808a(22) =3848a(23) =5132a(24) =6945a(25) =9192a(26) =12298a(27) =16178a(28) =21422a(29) =28000