375122domain: NAppears in sequencesNumber of Hamiltonian paths in P_4 X P_n.at n=9A003695a(n) = 2*a(n-1) - a(n-3) for n >= 5, a(0) = 2, a(1) = 4, a(2) = 7, a(3) = 12, a(4) = 22.at n=24A289107