67868domain: NAppears in sequencesNumber of irreducible indecomposable spherical curves with n crossings (only ordinary double points), the circle is oriented, the sphere is not oriented (OU case).at n=12A007756G.f. A(x) = 1 / (1 - x^a(0) / (1 - x^a(1) / (1 - x^a(2) / ... ))).at n=15A213411