421 и 842
421 = 400 + 20 + 1
842 = 800 + 40 + 2
842 < 421
842/2 = 421
12, 13, 14, 11, 21, 22, 23, 24, 31, 32, 33, 34, 41, 42, 43, 44. Всего 16 чисел.