title: Matching Number sequences in haskell
body: <p>my task is to match the number sequences of the numbers 5,7 and 9 in a list in Haskell. The list must be infinite, so that the following is possible:</p>
  
  <p>take 10 seq
  [5,7,9,10,14,15,18,20,21,25]</p>
  
  <p>I already figured out how to create an infinite sequence list of a single number:</p>
  
  <pre><code>    sevens :: [Int]
      sevens = sevens : (map (+7) sevens)
  </code></pre>
  
  <p>This works but how do I do this with multiple numbers (5,7 and 9 in this case)?</p>
  
  <p>Thanks for your help :)</p>