Number of unrooted triangulations with reflection symmetry of a quadrilateral with n internal nodes.

A005505

Number of unrooted triangulations with reflection symmetry of a quadrilateral with n internal nodes.

Terms

    a(0) =1a(1) =2a(2) =4a(3) =10a(4) =29a(5) =86a(6) =266a(7) =844a(8) =2742a(9) =9032a(10) =30202a(11) =101988a(12) =347914a(13) =1195500a(14) =4138310a(15) =14405848a(16) =50428392a(17) =177321636a(18) =626250990a(19) =2219876580a(20) =7896651847a(21) =28176271634a(22) =100830069380a(23) =361757157484

External references