“…Evaluate m n := M k 2 n−kn+k (mod k) for k = p t , where p is a prime number and t ≥ 3. It seems that the sequence (m n ) n≥0 is always periodic for any p and t. Computer calculation has provided the initial values: (m n ) n≥0 = (1, 1, 5, 5, 1, 1, 5, 5, · · · ) for k = 2 3 , (m n ) n≥0 = (1, 1, 10, 1, 1, 10, 1, 1, 10 · · ·) for k = 3 3 , (m n ) n≥0 = (1, 1, 126, 376, 126, 1, 1, 126, 376, 126, · · ·) for k = 5 4 , (m n ) n≥0 = (1,1,13,5,9,9,5,13,1,1,13,5,9,9,5,13, · · ·) for k = 2 4 .…”