“…Suppose n ≥ 2, t ≥ 0, (n, t) = (8, 3), (9,3), (9,4), (9,6), (9,7) and suppose H(n, t) = 1. Then H(n, t) is finite if and only if t = 0, 1 or (n, t) = (2k, k + 1) where k ≥ 1 (in which case H(n, t) ∼ = Z 2 k +1 ), or (n, t) = (3, 2), (4, 2), (5, 2), (5, 3), (5,4), (6,3), (7,4), (7,6).…”