Sequences of B-trees of order 3 with n labeled leaves.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =8a(5) =17a(6) =35a(7) =73a(8) =152a(9) =316a(10) =659a(11) =1376a(12) =2875a(13) =6004a(14) =12535a(15) =26173a(16) =54654a(17) =114134a(18) =238348a(19) =497743a(20) =1039432a(21) =2170634a(22) =4532949a(23) =9466295a(24) =19768943a(25) =41284768a(26) =86218046a(27) =180056039a(28) =376025957a(29) =785286555