27739833228domain: NAppears in sequencesNumber of walks on cubic lattice starting and finishing on the xy plane and never going below it.at n=15A005572a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ...+ a(n-1)*a(1) for n >= 3, with initial terms 2,1.at n=16A025228