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<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JS Alphabet Pattern 14 - Try It</title>
</head>
<body>
  <h1>Odd-Length Alphabet Triangle (A, ABC, ABCDE, ...)</h1>
  <p>Edit the ending letter or loops, then click Run.</p>
  <pre id="output"></pre>
  <script>
    const base = "A".charCodeAt(0);
    const last = "I".charCodeAt(0);
    let result = "";

    for (let i = base; i <= last; i += 2) {
      let line = "";
      for (let j = base; j <= i; j++) {
        line += String.fromCharCode(j);
      }
      result += line + "\n";
    }

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

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JavaScript Alphabet Pattern 14 (Try It)