A Note on the Middle Levels Conjecture

The middle levels conjecture asserts that there is a Hamiltonian cycle in the middle two levels of 2k + 1-dimensional hypercube. The conjecture is known to be true for k ≤ 17 [I. Shields, B.J. Shields and C.D. Savage, Disc. Math., 309, 5271–5277 (2009)]. In this note, we verify that the conjecture is also true for k = 18 by constructing a Hamiltonian cycle in the middle two levels of 37-dimensional hypercube with the aid of the computer. We achieve this by introducing a new decomposition technique and an efficient algorithm for ordering the Narayana objects.