Number of hexagonal n-element polyominoes whose graph is a path.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =10a(5) =24a(6) =67a(7) =182a(8) =520a(9) =1474a(10) =4248a(11) =12196a(12) =35168a(13) =101226a(14) =291565a(15) =838764a(16) =2412033a(17) =6929754a(18) =19896915a(19) =57084939a(20) =163677686a(21) =469008353a(22) =1343165478a(23) =3844533186a(24) =10998790991a(25) =31451726513a(26) =89899650912a(27) =256859865260a(28) =733620238080