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

A005507

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

Terms

    a(0) =2a(1) =6a(2) =18a(3) =52a(4) =166a(5) =524a(6) =1722a(7) =5664a(8) =19072a(9) =64408a(10) =220676a(11) =758864a(12) =2634734a(13) =9180872a(14) =32208376a(15) =113371636a(16) =401067522a(17) =1423073892a(18) =5068961452a(19) =18103192360a(20) =64853607912a(21) =232872927444a(22) =838311889890

External references