Respuestas

2013-03-13T02:41:39+01:00

16 = {2, 4, 8, 16} 
17 = {17} 
18 = {2, 3, 6, 9, 18} 
19 = {19} 
20 = {2, 4, 5, 10, 20}

15 3 15
2013-03-13T02:48:45+01:00

16: 1-2-4-8-16

17: 1-17

18: 1-2-3-9-18

19: 1-19

20: 1-2-4-5-10-20

espero que te sirva!