Number of symmetric unrooted self-avoiding walks of n steps on hexagonal lattice.

Terms

a(0) =1a(1) =3a(2) =4a(3) =12a(4) =18a(5) =50a(6) =78a(7) =208a(8) =337a(9) =867a(10) =1440a(11) =3613a(12) =6133a(13) =15058a(14) =26037a(15) =62756a(16) =110274a(17) =261524a(18) =466183a(19) =1089717a(20) =1967725a(21) =4540103a(22) =8294946a(23) =18913123a(24) =34929064a(25) =78778601a(26) =146943175a(27) =328097471a(28) =617667052a(29) =1366311508