Rotation distance between binary trees on n nodes.

Terms

a(0) =0a(1) =1a(2) =2a(3) =4a(4) =5a(5) =7a(6) =9a(7) =11a(8) =12a(9) =15a(10) =16a(11) =18a(12) =20a(13) =22a(14) =24a(15) =26a(16) =28a(17) =30a(18) =32a(19) =34a(20) =36a(21) =38a(22) =40a(23) =42a(24) =44a(25) =46a(26) =48a(27) =50a(28) =52a(29) =54