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本帖最后由 欧拉计划 于 2016-8-31 23:09 编辑
Exploring Pascal's triangle
We can easily verify that none of the entries in the first seven rows of Pascal's triangle are divisible by 7:
However, if we check the first one hundred rows, we will find that only 2361 of the 5050 entries are not divisible by 7.
Find the number of entries which are not divisible by 7 in the first one billion (109) rows of Pascal's triangle.
题目:
可以轻易验证,在帕斯卡三角形的前七行中没有任何数可以被 7 整除:
但是如果我们查看前 100 行,在 5050 个数中,一共有 2361 个不能被 7 整除。
求在帕斯卡三角形的前 109 行中共有多少个数不能被 7 整除。
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