Number of shapes of left-leaning height-balanced AVL trees with n (inner) nodes.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =2a(6) =2a(7) =2a(8) =3a(9) =5a(10) =7a(11) =9a(12) =11a(13) =13a(14) =17a(15) =26a(16) =42a(17) =66a(18) =97a(19) =134a(20) =180a(21) =241a(22) =321a(23) =424a(24) =564a(25) =774a(26) =1111a(27) =1661a(28) =2545a(29) =3925