Problem 12--(c)

Problem 12
08 March 2002

The sequence of triangle numbers is generated by adding the natural numbers. So the 7^(th) 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?

Answer:
76576500
code:
#include
#include
int main(void)
{
long int result=0;
long int i=1;
int counter=0;
while(counter<=500)
{
result+=i;
i++;
counter=0;
long int j;
long int k=sqrt(result);
for(j=1;j {
if(result%j==0)
{
counter+=2;
}
}
if(result==k*k) counter++;
}
printf("%ld\n",result);
return 0;
}