136994domain: NAppears in sequencesa(n) = a(1)*a(n-1) + a(2)*a(n-2) + ...+ a(n-1)*a(1) for n >= 5, with initial values 0,0,1,1.at n=29A025277Number of ordered trees with n edges such that non-leaf vertices at even levels have outdegree 1 and those at odd levels have outdegree 2.at n=27A248100