The sequence of triangle numbers is generated by adding the natural numbers. So the 7th triangle number would be 1 + 2 + 3 + 4 + 5 + 6 + 7 = 28. The first ten terms would be:
1, 3, 6, 10, 15, 21, 28, 36, 45, 55, ...
Let us list the factors of the first seven triangle numbers:
1: 1
3: 1,3
6: 1,2,3,6
10: 1,2,5,10
15: 1,3,5,15
21: 1,3,7,21
28: 1,2,4,7,14,28
We can see that 28 is the first triangle number to have over five divisors.
What is the value of the first triangle number to have over five hundred divisors?
查找能除尽的数的个数,递增至开方 每能除尽一个既有相对应的一个大的 所以为一对 ,能被开方时重复加了一个 。
#include <stdio.h> #include <math.h> int divisor(int a) { int i; int num=0; for(i=1;i<=sqrt(a);i++) { if(0 == a%i) num+=2; if(i*i == a) num--; } return num; } int main() { int i=1; int num=0; while(num<=500) { i++; num = divisor(i*(i+1)/2); } printf("%d\n",i*(i+1)/2); return 0; }
时间: 2024-10-30 01:10:22