Number of trees of diameter 4.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =1a(5) =2a(6) =5a(7) =8a(8) =14a(9) =21a(10) =32a(11) =45a(12) =65a(13) =88a(14) =121a(15) =161a(16) =215a(17) =280a(18) =367a(19) =471a(20) =607a(21) =771a(22) =980a(23) =1232a(24) =1551a(25) =1933a(26) =2410a(27) =2983a(28) =3690a(29) =4536