Number of connected outerplanar graphs on n unlabeled nodes.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =13a(5) =46a(6) =172a(7) =777a(8) =3783a(9) =20074a(10) =111604a(11) =646409a(12) =3846640a(13) =23410035a(14) =144965988a(15) =910898943a(16) =5794179218a(17) =37248630398a(18) =241676806702