function triangle(o) {
    var n = 1 << o,
        line = new Array(2 * n),
        i, j, t, u;
    for (i = 0; i < line.length; ++i) line[i] = '&nbsp;';
    line[n] = '*';
    for (i = 0; i < n; ++i) {
        document.write(line.join('') + "\n");
        u = '*';
        for (j = n - i; j < n + i + 1; ++j) {
            t = (line[j - 1] == line[j + 1] ? '&nbsp;' : '*');
            line[j - 1] = u;
            u = t;
        }
        line[n + i] = t;
        line[n + i + 1] = '*';
    }
}
document.write("<pre>\n");
triangle(6);
document.write("</pre>");