fun hailstone ← List by int n
  List h ← int[n]
  while n ≠ 1
    n ← when((n % 2 æ 0), n / 2, 3 * n + 1)
    h.append(n)
  end
  return h
end
int NUMBER ← 27
int LESS_THAN ← 100000
List sequence ← hailstone(NUMBER)
writeLine("The hailstone sequence for the number " + NUMBER +
  " has " + sequence.length + " elements")
writeLine("starting with " +
  sequence.extractStart(4).join(", ") + " and ending with " +
  sequence.extractEnd(4).join(", ") + ".")
int number ← 0
sequence ← int[]
for int i ← 1; i < LESS_THAN; ++i
  List current ← hailstone(i)
  if current.length > sequence.length
    sequence ← current
    number ← i
  end
end
writeLine("The number less than 100000 with longest hailstone sequence is " +
  number + ", with length of " + sequence.length + ".")