Trails of length n on honeycomb lattice.

Terms

a(0) =1a(1) =3a(2) =6a(3) =12a(4) =24a(5) =48a(6) =96a(7) =186a(8) =360a(9) =696a(10) =1344a(11) =2562a(12) =4872a(13) =9288a(14) =17664a(15) =33384a(16) =63120a(17) =119280a(18) =225072a(19) =423630a(20) =797400a(21) =1499256a(22) =2817216a(23) =5286480a(24) =9918768a(25) =18592080a(26) =34840848a(27) =65228874a(28) =122105496a(29) =228402168