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

Terms

a(0) =1a(1) =2a(2) =4a(3) =9a(4) =22a(5) =56a(6) =147a(7) =388a(8) =1047a(9) =2806a(10) =7600a(11) =20437a(12) =55313a(13) =148752a(14) =401629a(15) =1078746a(16) =2905751a(17) =7793632a(18) =20949045a(19) =56112530a(20) =150561752a(21) =402802376a(22) =1079193821a(23) =2884195424a(24) =7717665979a(25) =20607171273a(26) =55082560423a(27) =146961482787a(28) =392462843329