Number of rooted projective plane trees with n nodes.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =9a(5) =21a(6) =56a(7) =155a(8) =469a(9) =1480a(10) =4882a(11) =16545a(12) =57384a(13) =202060a(14) =720526a(15) =2593494a(16) =9408469a(17) =34350507a(18) =126109784a(19) =465200333a(20) =1723346074a(21) =6408356210a(22) =23911272090a(23) =89495909409a(24) =335916761128