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Problem 598


Problem 598


Split Divisibilities

Consider the number 48.
There are five pairs of integers a and b (ab) such that a×b=48: (1,48), (2,24), (3,16), (4,12) and (6,8).
It can be seen that both 6 and 8 have 4 divisors.
So of those five pairs one consists of two integers with the same number of divisors.

In general:
Let C(n) be the number of pairs of positive integers a×b=n, (ab) such that a and b have the same number of divisors;
so C(48)=1.

You are given C(10!)=3: (1680, 2160), (1800, 2016) and (1890,1920).

Find C(100!).


分配整除性

考虑数48。
有五对整数abab)满足a×b=48:(1,48),(2,24),(3,16),(4,12)和(6,8)。
可以看出,6和8都有4个因数。
所以在这五对整数中,只有一对整数的因数数量相同。

一般地:
C(n)表示所有满足a×b=nab),且ab的因数数量相同的正整数数对的数目;
因此已知C(48)=1

此外,还已知C(10!)=3:(1680, 2160),(1800, 2016)和(1890,1920)。

C(100!)


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