Выписать множину одноцыфровых чисел 20.8. 19.0.14.6.13.10. 17.11.

1. Единица со всеми взаимно проста.

2. Раскладываете каждое число из оставшихся на простые множители.

3. Для каждого числа находите большие его числа, не имеющие с ним общих простых множителей.

Т. о. получаете:

1 - 1,2, ... 20

2 - 3, 5, 7, все нечетные

3 - 4, 5, 7, 8, 10, 11, ... 19

4 - все нечетные

И так далее

Вот все пары:

{{1, 1}, {1, 2}, {1, 3}, {1, 4}, {1, 5}, {1, 6}, {1, 7}, {1, 8}, {

1, 9}, {1, 10}, {1, 11}, {1, 12}, {1, 13}, {1, 14}, {1, 15}, {1,

16}, {1, 17}, {1, 18}, {1, 19}, {1, 20}, {2, 1}, {2, 3}, {2, 5}, {2,

7}, {2, 9}, {2, 11}, {2, 13}, {2, 15}, {2, 17}, {2, 19}, {3,

1}, {3, 2}, {3, 4}, {3, 5}, {3, 7}, {3, 8}, {3, 10}, {3, 11}, {3,

13}, {3, 14}, {3, 16}, {3, 17}, {

3, 19}, {3, 20}, {4, 1}, {4, 3}, {4, 5}, {4, 7}, {4, 9}, {4, 11}, {4,

13}, {4, 15}, {4, 17}, {4, 19}, {5, 1}, {5, 2}, {5, 3}, {5, 4}, {5, 6}, {

5, 7}, {5, 8}, {5, 9}, {5,

11}, {5, 12}, {5, 13}, {5, 14}, {5, 16}, {5, 17}, {5, 18}, {5,

19}, {6, 1}, {6,

5}, {6, 7}, {6, 11}, {6, 13}, {6, 17}, {6, 19}, {7, 1}, {7,

2}, {7, 3}, {7, 4}, {7, 5}, {7, 6}, {7, 8}, {7, 9}, {7, 10}, {7,

11}, {7, 12}, {7, 13}, {7, 15}, {7, 16}, {7, 17}, {

7, 18}, {7, 19}, {7, 20}, {8, 1}, {8, 3}, {8, 5}, {8,

7}, {8, 9}, {8, 11}, {8, 13}, {8, 15}, {8, 17}, {8, 19}, {9, 1}, {

9, 2}, {9, 4}, {9, 5}, {9, 7}, {9, 8}, {9, 10}, {9, 11}, {9, 13}, {9,

14}, {9, 16}, {9, 17}, {9, 19}, {9, 20}, {10, 1}, {10, 3}, {

10, 7}, {10, 9}, {10, 11}, {

10, 13}, {10, 17}, {10, 19}, {11, 1}, {11, 2}, {11, 3}, {11, 4}, {

11, 5}, {11, 6}, {11, 7}, {11, 8}, {11, 9}, {11, 10}, {11, 12}, {11,

13}, {11, 14}, {11, 15}, {11, 16}, {11, 17}, {11, 18}, {11, 19}, {11,

20}, {12, 1}, {12, 5}, {12, 7}, {12,

11}, {12, 13}, {12, 17}, {12, 19}, {13, 1}, {13, 2}, {13,

3}, {13, 4}, {13, 5}, {13, 6}, {13, 7}, {13, 8}, {13, 9}, {13, 10}, {

13, 11}, {13, 12}, {13, 14}, {13, 15}, {13, 16}, {13, 17}, {

13, 18}, {13, 19}, {13, 20}, {14, 1}, {14, 3}, {14, 5}, {

14, 9}, {14, 11}, {14, 13}, {14, 15}, {14, 17}, {14, 19}, {15, 1}, {

15, 2}, {15, 4}, {15, 7}, {15, 8}, {15, 11}, {15, 13}, {15, 14}, {15, 16}, {

15, 17}, {

15, 19}, {16, 1}, {16, 3}, {16, 5}, {16, 7}, {16, 9}, {16, 11}, {16,

13}, {16, 15}, {16, 17}, {16, 19}, {17, 1}, {17, 2}, {17, 3}, {17,

4}, {17, 5}, {17, 6}, {17, 7}, {17, 8}, {17, 9}, {17, 10}, {

17, 11}, {17, 12}, {17, 13}, {17, 14}, {17, 15}, {17, 16}, {

17, 18}, {17, 19}, {17, 20}, {18, 1}, {18, 5}, {18, 7}, {18,

11}, {18, 13}, {18, 17}, {18,

19}, {19, 1}, {19, 2}, {19, 3}, {19, 4}, {19, 5}, {19, 6}, {19, 7}, {19, /

8}, {19, 9}, {19, 10}, {19, 11}, {19, 12}, {19,

13}, {19, 14}, {19, 15}, {19, 16}, {

19, 17}, {19, 18}, {19, 20}, {20, 1}, {20, 3}, {20, 7}, {20, 9}, {

20, 11}, {20, 13}, {20, 17}, {20, 19}}