C++ :

#include <cstdio>
#include <cstring>
/* n<=7 -> 边长 3^6 = 729，留足余量 */
static char g[800][800];
void draw(int n, int r, int c){
    if(n == 1){ g[r][c] = 'X'; return; }
    int u = 1; for(int i=2;i<n;i++) u *= 3;   /* u = 3^(n-2) */
    draw(n-1, r, c);
    draw(n-1, r, c + 2*u);
    draw(n-1, r + u, c + u);
    draw(n-1, r + 2*u, c);
    draw(n-1, r + 2*u, c + 2*u);
}
int main(){
    int n; if(scanf("%d", &n) != 1) return 0;
    int s = 1; for(int i=1;i<n;i++) s *= 3;
    memset(g, ' ', sizeof(g));
    draw(n, 0, 0);
    for(int i=0;i<s;i++){
        int last = -1;
        for(int j=0;j<s;j++) if(g[i][j] == 'X') last = j;
        for(int j=0;j<=last;j++) putchar(g[i][j]);
        putchar('\n');
    }
    return 0;
}