Number of n-step walks on square lattice, self-avoiding until the last step.

Terms

a(0) =0a(1) =0a(2) =4a(3) =12a(4) =44a(5) =116a(6) =356a(7) =948a(8) =2772a(9) =7396a(10) =20972a(11) =56108a(12) =156236a(13) =418228a(14) =1151556a(15) =3081180a(16) =8421052a(17) =22514652a(18) =61207972a(19) =163518308a(20) =442769316a(21) =1181982628a(22) =3190663628a(23) =8511628124a(24) =22920057932a(25) =61104234356a(26) =164212633412