Sum of k-Mirror Numbers
<p>A <strong>k-mirror number</strong> is a <strong>positive</strong> integer <strong>without leading zeros</strong> that reads the same both forward and backward in base-10 <strong>as well as</strong> in base-k.</p>

<ul>
	<li>For example, <code>9</code> is a 2-mirror number. The representation of <code>9</code> in base-10 and base-2 are <code>9</code> and <code>1001</code> respectively, which read the same both forward and backward.</li>
	<li>On the contrary, <code>4</code> is not a 2-mirror number. The representation of <code>4</code> in base-2 is <code>100</code>, which does not read the same both forward and backward.</li>
</ul>

<p>Given the base <code>k</code> and the number <code>n</code>, return <em>the <strong>sum</strong> of the</em> <code>n</code> <em><strong>smallest</strong> k-mirror numbers</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> k = 2, n = 5
<strong>Output:</strong> 25
<strong>Explanation:
</strong>The 5 smallest 2-mirror numbers and their representations in base-2 are listed as follows:
  base-10    base-2
    1          1
    3          11
    5          101
    7          111
    9          1001
Their sum = 1 + 3 + 5 + 7 + 9 = 25. 
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> k = 3, n = 7
<strong>Output:</strong> 499
<strong>Explanation:
</strong>The 7 smallest 3-mirror numbers are and their representations in base-3 are listed as follows:
  base-10    base-3
    1          1
    2          2
    4          11
    8          22
    121        11111
    151        12121
    212        21212
Their sum = 1 + 2 + 4 + 8 + 121 + 151 + 212 = 499.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> k = 7, n = 17
<strong>Output:</strong> 20379000
<strong>Explanation:</strong> The 17 smallest 7-mirror numbers are:
1, 2, 3, 4, 5, 6, 8, 121, 171, 242, 292, 16561, 65656, 2137312, 4602064, 6597956, 6958596
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>2 &lt;= k &lt;= 9</code></li>
	<li><code>1 &lt;= n &lt;= 30</code></li>
</ul>
Math; Enumeration
function kMirror(k: number, n: number): number {
    function check(x: number, k: number): boolean {
        const s: number[] = [];
        while (x > 0) {
            s.push(x % k);
            x = Math.floor(x / k);
        }
        for (let i = 0, j = s.length - 1; i < j; i++, j--) {
            if (s[i] !== s[j]) {
                return false;
            }
        }
        return true;
    }

    let ans = 0;
    for (let l = 1; ; l++) {
        const x = Math.pow(10, Math.floor((l - 1) / 2));
        const y = Math.pow(10, Math.floor((l + 1) / 2));
        for (let i = x; i < y; i++) {
            let v = i;
            let j = l % 2 === 0 ? i : Math.floor(i / 10);
            while (j > 0) {
                v = v * 10 + (j % 10);
                j = Math.floor(j / 10);
            }
            if (check(v, k)) {
                ans += v;
                n--;
                if (n === 0) {
                    return ans;
                }
            }
        }
    }
}
