Take the number 192 and multiply it by each of 1, 2, and 3:

192 1 = 192
192 2 = 384
192 3 = 576

By concatenating each product we get the 1 to 9 pandigital, 192384576. We will call 192384576 the concatenated product of 192 and (1,2,3)

The same can be achieved by starting with 9 and multiplying by 1, 2, 3, 4, and 5, giving the pandigital, 918273645, which is the concatenated product of 9 and (1,2,3,4,5).

What is the largest 1 to 9 pandigital 9-digit number that can be formed as the concatenated product of an integer with (1,2, ... , n) where n 1?

def p38_check(n)
  str=n.to_s
  i=1
  str+=(n*(i+=1)).to_s while(str.length<9)
  return false if(str.length>9)
  return false unless str.split("").sort.join("")=="123456789"
  return str.to_i
end

def p38
  largest=0
  (2...10000).each do |i|
    if jake=p38_check(i)
      largest=jake if jake>largest
    end
  end
  puts largest
end