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<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JS Number Pattern 21 - Try It</title>
</head>
<body>
  <h1>Staggered Number Triangle</h1>
  <p>Edit <code>rows</code> and click Run.</p>
  <pre id="output"></pre>

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

    for (let i = 1; i <= rows; i++) {
      // m controls the decreasing offset, k is the computed next number.
      let m = rows - 1;
      let k = i + m;
      let line = "" + i;

      for (let j = 1; j < i; j++) {
        line += " " + k;
        m--;
        k = k + m;
      }

      result += line + "\n";
    }

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

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JavaScript Number Pattern 21 (Try It)