Discription Let's denote d(n) as the number of divisors of a positive integer n. You are given three integers a, b and c. Your task is to calculate the following sum: Find the sum modulo 1073741824 (230). Input The first line contains three space-sep…

[codeforces 235]A. LCM Challenge 试题描述 Some days ago, I learned the concept of LCM (least common multiple). I've played with it for several times and I want to make a big number with it. But I also don't want to use many numbers, so I'll choose three…

http://codeforces.com/problemset/problem/235/E (题目链接) 题意 给出${a,b,c}$,求${\sum_{i=1}^a\sum_{j=1}^b\sum_{k=1}^cd(ijk)}$ extra 有这样一个公式,就是约数个数和那道题的推广吧.$${\sum_{i=1}^a\sum_{j=1}^b\sum_{k=1}^cd(ijk)=\sum_{i=1}^a\sum_{j=1}^b\sum_{k=1}^c[gcd(i,j)=gcd(i,k)=gcd…

dp(a,b,c,p) = sigma ( dp(a/p^i,b/p^j,c/p^k) * ( 1+i+j+k) ) 表示用小于等于p的素数去分解的结果有多少个 E. Number Challenge time limit per test 3 seconds memory limit per test 512 megabytes input standard input output standard output Let's denote d(n) as the number of divi…

Easy Number Challenge Time Limit:2000MS     Memory Limit:262144KB     64bit IO Format:%I64d & %I64u Submit Status Practice CodeForces 236B Appoint description:  System Crawler  (2016-04-26) Description Let's denote d(n) as the number of divisors of a…

Codeforces 55D Beautiful Number a positive integer number is beautiful if and only if it is divisible by each of its nonzero digits. Input The first line of the input contains the number of cases t (1 ≤ t ≤ 10). Each of the next t lines contains two…

B. Easy Number Challenge time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Let's denote d(n) as the number of divisors of a positive integer n. You are given three integers a, b and c. Your…

试题 算法训练 Number Challenge 资源限制 时间限制:3.0s 内存限制:512.0MB 问题描述 定义d(n)为n的约数个数.现在,你有三个数a,b,c.你的任务是计算下面式子modulo 1073741824 (2^30)的值. 输入格式 三个正整数a,b,c. 输出格式 一个数,即上面式子modulo 1073741824 (2^30)的值. 样例输入 2 2 2 样例输出 20 数据规模和约定 a, b , c (1 ≤ a, b, c ≤ 2000) import ja…

http://codeforces.com/contest/235/problem/E 远距离orz......rng_58 证明可以见这里(可能要FQ才能看到) 还是copy一下证明吧: 记 $$f(a,b,c)=\sum\limits_{i=1}^{a}\sum\limits_{j=1}^{b}\sum\limits_{k=1}^{c}d(ijk)$$ 和 $$g(a,b,c)=\sum\limits_{gcd(i,j)=gcd(j,k)=gcd(i,k)=1}\left \lfloor \…

https://www.luogu.org/problemnew/show/P3327 不会做. 去搜题解...为什么题解都用了一个奇怪的公式?太奇怪了啊... 公式是这样的: $d(xy)=\sum_{i|x}\sum_{j|y}[(i,j)=1]$ 证明:(转自:https://23613.blog.luogu.org/solution-p3327) 考虑一个质因子p,设x中p的指数为a,y中p的指数为b(指质因数分解结果中指数),那么根据因数个数定理,这个质因子对式子左边的贡献(指使得答案…