Number of 4-linear trees on n nodes.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =0a(8) =0a(9) =1a(10) =6a(11) =37a(12) =158a(13) =591a(14) =1896a(15) =5537a(16) =14812a(17) =37133a(18) =87841a(19) =198267a(20) =429199a(21) =896731a(22) =1814978a(23) =3572810a(24) =6858774a(25) =12874977a(26) =23679669a(27) =42752787a(28) =75887244a(29) =132618635