Guttmann's coefficients c_n rho_n for square lattice.

Terms

a(0) =4a(1) =32a(2) =164a(3) =704a(4) =2748a(5) =10096a(6) =35524a(7) =121056a(8) =402420a(9) =1311504a(10) =4205476a(11) =13304864a(12) =41612324a(13) =128878736a(14) =395767092a(15) =1206315296a(16) =3652739252a(17) =10995977424a(18) =32927997988a(19) =98139646880a(20) =291246749300a(21) =860965104720