Pretty sure the first one should be done with a closed form formula: lcm(3, 5) = 15. So there is a repeating cell of values every 15 which we can take advanta

Pretty sure the first one should be done with a closed form formula: lcm(3, 5) = 15. So there is a repeating cell of values every 15 which we can take advantage of: 0, 3, 5, 6, 9, 10, 12, + 15 -> 15, 18, 20, 21, 24, 25, 27, + 15 -> 30, 33, 35, 36, 39, 40, 42 The last cell ending in 1000 is incomplete.