有一串数如下:1,2,4,7,11,16········依次逐个产生这串数,直到产生第50个为止.这50个数中,被3除余1的数有几个?
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![有一串数如下:1,2,4,7,11,16········依次逐个产生这串数,直到产生第50个为止.这50个数中,被3除余1的数有几个?](/uploads/image/z/653450-50-0.jpg?t=%E6%9C%89%E4%B8%80%E4%B8%B2%E6%95%B0%E5%A6%82%E4%B8%8B%EF%BC%9A1%2C2%2C4%2C7%2C11%2C16%C2%B7%C2%B7%C2%B7%C2%B7%C2%B7%C2%B7%C2%B7%C2%B7%E4%BE%9D%E6%AC%A1%E9%80%90%E4%B8%AA%E4%BA%A7%E7%94%9F%E8%BF%99%E4%B8%B2%E6%95%B0%2C%E7%9B%B4%E5%88%B0%E4%BA%A7%E7%94%9F%E7%AC%AC50%E4%B8%AA%E4%B8%BA%E6%AD%A2.%E8%BF%9950%E4%B8%AA%E6%95%B0%E4%B8%AD%2C%E8%A2%AB3%E9%99%A4%E4%BD%991%E7%9A%84%E6%95%B0%E6%9C%89%E5%87%A0%E4%B8%AA%3F)
有一串数如下:1,2,4,7,11,16········依次逐个产生这串数,直到产生第50个为止.这50个数中,被3除余1的数有几个?
有一串数如下:1,2,4,7,11,16········依次逐个产生这串数,直到产生第50个为止.这50个数中,被3除余1的数有几个?
有一串数如下:1,2,4,7,11,16········依次逐个产生这串数,直到产生第50个为止.这50个数中,被3除余1的数有几个?
规律是每两个数相差1、2、3、4……
第n个数是1+1+2+……+(n-1)=1+n(n-1)/2
就是说n(n-1)/2能被3整除就行了
n=1、2、3、……50中,三个一组,因为三个就以循环了,每组都有两个使n(n-1)/2能被3整除,是第一三个
50/3=16余2
最后剩两个n=49能整除,50不行
所以是16*2+1=33
我不会啊
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