Intervals of balanced binary trees in the Tamari lattices.

Terms

a(0) =1a(1) =1a(2) =3a(3) =1a(4) =7a(5) =12a(6) =6a(7) =52a(8) =119a(9) =137a(10) =195a(11) =231a(12) =1019a(13) =3503a(14) =6593a(15) =12616a(16) =26178a(17) =43500a(18) =64157a(19) =94688a(20) =232560a(21) =817757a(22) =2233757a(23) =5179734a(24) =11676838a(25) =24867480a(26) =50465099a(27) =99805751a(28) =190508209a(29) =357754875