Number of inner dual graphs of planar polyhexes with n hexagons.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =8a(5) =21a(6) =53a(7) =151a(8) =458a(9) =1477a(10) =4918a(11) =16956a(12) =59494a(13) =212364a(14) =766753a(15) =2796876a(16) =10284793a(17) =38096072a(18) =141998218a(19) =532301941a(20) =2005638293a(21) =7592441954a(22) =28865031086a(23) =110174528925a(24) =422064799013