Number of unlabeled 7-trees on n nodes.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =1a(7) =1a(8) =1a(9) =2a(10) =5a(11) =15a(12) =64a(13) =342a(14) =2344a(15) =19137a(16) =181098a(17) =1922215a(18) =22472875a(19) =284556458a(20) =3849828695a(21) =54974808527a(22) =819865209740