“…, 9 22 3 1, 7, 49 28 2 2, 6, 18 28 8 1, 3, 9 33 3 1, 8, 64 34 2 1, 55, 3025 37 21 2, 22, 242 37 84 1, 11, 121 41 2 8, 20, 50 41 8 4, 10, 25 56 11 2, 10, 50 56 44 1, 5, 25 57 7 1, 4, 16 57 87 1, 8, 64 63 2 3, 9, 27 63 18 1, 3, 9 65 It is very surprising that the following theorem on linear relations on the solution set of Pell equations contains as a corollary an upper bound for three term arithmetic progressions (cf. [8,Theorem 1]) as well as an upper bound for three term geometric progressions (Theorem 1).…”