Coefficients A_lmn of the series development of the tidal potential vs. the obliquity of the circular planetary orbit for l = 9, m = 8, and n = 1 (solid red line), corresponding to the case of Kepler-17; l = 9, m = 8, and n = 3, corresponding to CoRoT-2 (dotted green line); l = 7, m = 6, and n = 1, corresponding to HAT-P-11 (dashed blue line); and l = 3, m = 1, and n = 1, corresponding to the synchronous systems CoRoT-4 and τ Boo (dash-dotted orange line).