Number of n-step tri-directional self-avoiding walks on the hexagonal lattice.

Terms

a(0) =1a(1) =3a(2) =9a(3) =21a(4) =51a(5) =123a(6) =285a(7) =669a(8) =1569a(9) =3603a(10) =8343a(11) =19335a(12) =44193a(13) =101577a(14) =233697a(15) =532569a(16) =1218345a(17) =2789475a(18) =6343161a(19) =14464101a(20) =33004269a(21) =74923059a(22) =170440203a(23) =387945747a(24) =879473277a(25) =1997066751a(26) =4536975315a(27) =10273846185