321 Raspunsul se obtine usor, 0 3 6 9 12 15 18 ... 960 = (3 * 0) (3 * 1) (3 * 2) (3 * 3) (3 * 4) (3 * 5) (3 * 6) ... (3 * 320), deci zunt 320 + 1 termeni