Number of line-rooted projective plane trees with n nodes.

Terms

a(0) =1a(1) =1a(2) =3a(3) =6a(4) =17a(5) =44a(6) =133a(7) =404a(8) =1319a(9) =4392a(10) =15114a(11) =52796a(12) =187410a(13) =671848a(14) =2430509a(15) =8852584a(16) =32438603a(17) =119463056a(18) =441926206a(19) =1641246060a(20) =6117011262a(21) =22871513128a(22) =85766691938a(23) =322479555096