Number of unrooted triangulations with reflection symmetry of a disk with 2 internal nodes and n+3 nodes on the boundary.

A005509

Number of unrooted triangulations with reflection symmetry of a disk with 2 internal nodes and n+3 nodes on the boundary.

Terms

    a(0) =1a(1) =4a(2) =7a(3) =18a(4) =26a(5) =68a(6) =91a(7) =248a(8) =318a(9) =900a(10) =1122a(11) =3278a(12) =4004a(13) =12012a(14) =14443a(15) =44304a(16) =52598a(17) =164424a(18) =193154a(19) =613700a(20) =714476a(21) =2302344a(22) =2659582a(23) =8677072a(24) =9954860a(25) =32836180a(26) =37442160a(27) =124715430a(28) =141430680a(29) =475237500

External references