41 - 3 = 38
38 / 2 = 19
19 - 3 = 16
16 / 2 = 8
8 / 2 = 4
Ответ: 21211
20 раз:
7, 17, 27, 37, 47, 57, 67, 87, 97
70, 71, 72, 73, 74, 75, 76, 77, 78, 79