41,42,...,80共40个数，最大的80都不到最小的41的2倍。所以40不对。
还得用抽屉原理说明41可以，
穷举法把1~80划入40个集合，....
{1,2,4,8,16,32,64}---1个
{3,6,12,24,48}
{5,10,20,40,80}---2个
{7,14,28,56}
{9,18,36,72}---2个
{11,22,44}
{13,26,52}
{15,30,60}
{17,34,68}
{19,38,76}---5个
{21,42}
{23,46}
{25,50}
{27,54}
{29,58}
{31,62}
{33,66}
{35,70}
{37,74}
{39,78}---10个
{41}，{43},.....,{79}---20个 |
