Number of bipartite outerplanar graphs on n unlabeled nodes.

Terms

a(0) =1a(1) =2a(2) =3a(3) =7a(4) =12a(5) =29a(6) =61a(7) =162a(8) =412a(9) =1221a(10) =3665a(11) =12031a(12) =40514a(13) =143244a(14) =518247a(15) =1926638a(16) =7285835a(17) =28013935a(18) =109058879a(19) =429366751