63 People Ionian Sea Safely Rescued Cruise Ship Norwegian Line Rescues In The

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缺失的数是31。分析如下：数列规律：这个数列的规律在于相邻两项之间的差值是2的幂次方。具体来说，7与3的差是4，15与7的差是8，以此类推。差值计算： 3到7的差是4.

Cruise Ship Rescues 63 People From Overcrowded Sailboat In The Ionian Sea