Number of polyhexes of class PF2 with a particular symmetry.

Terms

a(0) =0a(1) =0a(2) =1a(3) =4a(4) =17a(5) =66a(6) =269a(7) =1102a(8) =4635a(9) =19768a(10) =85659a(11) =375524a(12) =1664015a(13) =7438862a(14) =33515027a(15) =152016610a(16) =693622315a(17) =3181516040a(18) =14661568795a(19) =67850245684a(20) =315187594779