question about nested for loop

0 -> 1
1 -> 3
2 -> 5
3 -> 3
4 -> 1

#include <stdio.h>

int abs(int n) {
	return n > 0 ? n : -n;
}

int main() {
	for (int i = 0; i < 5; ++i) {
		int max = 5 - abs(i - 2) * 2; //Our equation
		for (int j = 0; j < max; ++j) {
			putchar('*');
		}
		putchar('\n'); //Print the new line
	}
	return 0;
}

void pyramid(unsigned short height) {
   char* line = new char[height+1];   // allocate output string
   char* p = line+height;             // position at end
   *p = 0;                            // set end of string marker
   while (p != line) {                // iterate to start of string ...
      *--p = '*';                     // ... and fill while doing so
      puts(p);                        // print the filled-in part
   }
   while (*++p) {                     // iterate back to end of string
      puts(p);                        // print to end of string
   }
   delete [] line;                    // release string memory
}