Number of trees of diameter 6.

Terms

a(0) =1a(1) =3a(2) =11a(3) =29a(4) =74a(5) =167a(6) =367a(7) =755a(8) =1515a(9) =2931a(10) =5551a(11) =10263a(12) =18677a(13) =33409a(14) =59024a(15) =102984a(16) =177915a(17) =304458a(18) =516939a(19) =871180a(20) =1458882a(21) =2428548a(22) =4021670a(23) =6627515a(24) =10874462a(25) =17770474a(26) =28932739a(27) =46943967a(28) =75925797a(29) =122433291