Total diameter of unlabeled trees with n nodes.

Terms

a(0) =0a(1) =1a(2) =2a(3) =5a(4) =9a(5) =21a(6) =44a(7) =103a(8) =232a(9) =571a(10) =1368a(11) =3441a(12) =8653a(13) =22263a(14) =57518a(15) =150733a(16) =396937a(17) =1054540a(18) =2815453a(19) =7562159a(20) =20399714a(21) =55280532a(22) =150356806a(23) =410432671a(24) =1123902587a(25) =3086827578a(26) =8500975970a(27) =23470712241a(28) =64952794778a(29) =180144093389