def foo(n):
	# stackoverflow.com/a/4601480/849891
  p2 = 1 # current power of 2
  p3 = 1 # current power of 3
  e3 = 0 # exponent of current power of 3
  t = 1 # number less than or equal to the current power of 2
  while t < n:
    p2 *= 2
    if p3 * 3 < p2:
      p3 *= 3
      e3 += 1
    t += 1 + e3
  candidates = [p2]
  c = p2
  for i in range(e3):
    c /= 2
    c *= 3
    if c > p2: c /= 2
    candidates.append(c)
  return sorted(candidates)[n - (t - len(candidates))] 
 
print( foo(100))
print( foo(10000))
print( foo(1000))

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