Number of n-step self-avoiding walks on three quadrants of a 2D square lattice.

Terms

a(0) =1a(1) =4a(2) =10a(3) =28a(4) =74a(5) =202a(6) =534a(7) =1442a(8) =3822a(9) =10258a(10) =27202a(11) =72718a(12) =192840a(13) =514228a(14) =1363342a(15) =3629316a(16) =9619264a(17) =25575326a(18) =67765590a(19) =180001304a(20) =476807826a(21) =1265567600a(22) =3351529410a(23) =8890447682a(24) =23538665948a(25) =62409037914a(26) =165202281046