title: Regular expression to Star with number and then numbers or one letter
body: <p>I have this regular expression</p>
  
  <pre><code>^[0-9]+[a-zA-Z0-9]*
  </code></pre>
  
  <p>But I need one that always stars with a number then it can be another number or a letter, but it can not be number letter number. The letter will always be the last. Like this example</p>
  
  <pre><code>102A OK
  1A OK
  2  OK
  110 OK
  10A1 WRONG
  BV WRONG
  </code></pre>
  
  <p>The letter cannot be between two numbers. </p>