triangle.c

#include <stdio.h>
#include <stdlib.h>

void triangle(int, int);

int main(int argc, char **argv)
{
  triangle(atoi(argv[1]), 0); // 17
  return 0;
}

void triangle(int times, int indentation)
{
  if (times <= 0)
    return;

  if (indentation > 0)
    printf("%*c", indentation, ' ');

  for (int i = 0; i < times; i++)
    putchar('*');

  putchar('\n');
  triangle(times-2, indentation+1);
}