Project Euler - Problem 28

28.c

#include <stdio.h>
#define ROWS 1001

int main() {
	int levels;
	int sum = 0;
	int corner = 1;
	int row_length = 2;
	for(levels = 0; levels < ROWS/2; ++levels) {
		sum += (2*corner + row_length*3)*2;
		corner += 4*row_length;
		row_length += 2;
	}
	sum += corner;
	printf("The answer is %d\n", sum);
}