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Problem 111


Problem 111


Primes with runs

Considering 4-digit primes containing repeated digits it is clear that they cannot all be the same: 1111 is divisible by 11, 2222 is divisible by 22, and so on. But there are nine 4-digit primes containing three ones:

1117, 1151, 1171, 1181, 1511, 1811, 2111, 4111, 8111

We shall say that M(n, d) represents the maximum number of repeated digits for an n-digit prime where d is the repeated digit, N(n, d) represents the number of such primes, and S(n, d) represents the sum of these primes.

So M(4, 1) = 3 is the maximum number of repeated digits for a 4-digit prime where one is the repeated digit, there are N(4, 1) = 9 such primes, and the sum of these primes is S(4, 1) = 22275. It turns out that for d = 0, it is only possible to have M(4, 0) = 2 repeated digits, but there are N(4, 0) = 13 such cases.

In the same way we obtain the following results for 4-digit primes.

Digit, d M(4, d) N(4, d) S(4, d)
0 2 13 67061
1 3 9 22275
2 3 1 2221
3 3 12 46214
4 3 2 8888
5 3 1 5557
6 3 1 6661
7 3 9 57863
8 3 1 8887
9 3 7 48073

For d = 0 to 9, the sum of all S(4, d) is 273700.

Find the sum of all S(10, d).


有重复数字的素数

考虑一个有重复数字的4位素数,显然这4个数字不能全都一样:1111被11整除,2222被22整除,依此类推;但是,有9个4位素数包含有三个一:

1117, 1151, 1171, 1181, 1511, 1811, 2111, 4111, 8111

我们记M(n, d)是n位素数中数字d重复出现的最多次数,N(n, d)是这类素数的个数,而S(n, d)是这类素数的和。

因此M(4, 1) = 3是4位素数中数字1重复出现的最多次数,有N(4, 1) = 9个这类素数,而它们的和是S(4, 1) = 22275。还能得出,对于d = 0,在4位素数中最多重复出现M(4, 0) = 2次,但是有N(4, 0) = 13个这类素数。

同样地,我们可以得到4位素数的如下结果。

数字d M(4, d) N(4, d) S(4, d)
0 2 13 67061
1 3 9 22275
2 3 1 2221
3 3 12 46214
4 3 2 8888
5 3 1 5557
6 3 1 6661
7 3 9 57863
8 3 1 8887
9 3 7 48073

对于d = 0至9,所有S(4, d)的和为273700。

求所有S(10, d)的和。