title: Regular Expression for credit card verification
body: <p>I need to verify a credit card (dummy - i'm not doing any transaction in real). The conditions are </p>
  
  <ol>
  <li><p>It has to be between 10 and 16 digits.</p></li>
  <li><p>Start with a digit 3 or 4</p></li>
  <li><p>Only digits are allowed i mean [0-9].</p></li>
  </ol>
  
  <p>I tried it and mine was [3-4][0-9]{10-16}. But it seems to be not yielding results.</p>
  
  <p>Thank you in anticipation</p>