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<html>
<head>
  <meta charset="utf-8">
  <title>JS Number Pattern 22 - Try It</title>
</head>
<body>
  <h1>Odd Length Number Triangle</h1>
  <p>Edit <code>rows</code> and click Run.</p>
  <pre id="output"></pre>

  <script>
    const rows = 5;
    let result = "";

    // Outer loop uses odd lengths: 1, 3, 5, 7, 9...
    for (let i = 1; i <= 2 * rows - 1; i += 2) {
      let line = "";

      // Concatenate digits without spaces.
      for (let j = 1; j <= i; j++) {
        line += j;
      }

      result += line + "\n";
    }

    document.getElementById("output").textContent = result;
  </script>
</body>
</html>

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JavaScript Number Pattern 22 (Try It)