Number of polyhexes of class PF2 with C_{2n} symmetry.

Terms

a(0) =0a(1) =1a(2) =5a(3) =20a(4) =82a(5) =335a(6) =1402a(7) =5949a(8) =25652a(9) =111963a(10) =494157a(11) =2201270a(12) =9886034a(13) =44712737a(14) =203489627a(15) =931191850a(16) =4282171470a(17) =19778577235a(18) =91715812335a(19) =426824400684