Number of P-graphs with 2n edges.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =8a(5) =14a(6) =42a(7) =79a(8) =252a(9) =494a(10) =1636a(11) =3294a(12) =11188a(13) =22952a(14) =79386a(15) =165127a(16) =579020a(17) =1217270a(18) =4314300a(19) =9146746a(20) =32697920a(21) =69799476a(22) =251284292a(23) =539464358a(24) =1953579240a(25) =4214095612a(26) =15336931928a(27) =33218794236a(28) =121416356108