Filename with two dots

eloquentjavascript-03.00.litcoffee

http://eloquentjavascript.net/2nd_edition/preview/03_functions.html
Consider this puzzle: by starting from the number 1 and repeatedly either adding 5 or multiplying by 3, an infinite amount of new numbers can be produced. How would you write a function that, given a number, tries to find a sequence of such additions and multiplications that produce that number? For example, the number 13 could be reached by first multiplying by 3 and then adding 5 twice, whereas the number 15 cannot be reached at all.

Here is a recursive CoffeeScript solution:

findSolution = (target) ->
  find = (start, history) ->
    if start is target
      history
    else if start > target
      null
    else
      find(start + 5, "(#{history} + 5)") or find(start * 3, "(#{history} * 3)")
  find 1, "1"
console.log findSolution(24)