Number of catafusenes with 2n hexagons and C symmetry.

Terms

a(0) =0a(1) =0a(2) =1a(3) =5a(4) =22a(5) =97a(6) =408a(7) =1752a(8) =7535a(9) =32895a(10) =144816a(11) =644058a(12) =2886967a(13) =13037352a(14) =59248959a(15) =270799903a(16) =1243939278a(17) =5740014143a(18) =26594306442a(19) =123668622726a(20) =577003771681