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    "# An Introduction to Python\n",
    "## Loops\n",
    "\n",
    "### This notebook contains the programming exercises for [An Introduction to Python: Loops.](https://www.youtube.com/watch?v=NoVoGis_v2M)\n",
    "\n"
   ]
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   "source": [
    "# Exercises\n",
    "## Do the following problems."
   ]
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   "source": [
    "### Jupyter Notebook Shortcuts:\n",
    "\n",
    "There are two modes when a cell is highlighted. \n",
    "\n",
    "#### Command Mode: Press ESC to activate. The cell has a blue border if this mode is active. In this mode, you can add, delete, create, copy and paste cells.\n",
    "\n",
    "- create a new cell above the current cell: a\n",
    "- create a new cell below the current cell: b\n",
    "- delete the current cell: dd\n",
    "- change the current cell’s type to “Code”: y\n",
    "- change the current cell’s type to “Markdown”: m\n",
    "\n",
    "#### Edit Mode: Press ENTER to activate. The cell has a green border if this mode is active. In this mode, you can edit and type text into the cell.\n",
    "\n",
    "- execute the current cell and create a new cell: SHIFT + ENTER"
   ]
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   "source": [
    "#### Provide an equivalent Python range() expression for each of the following integer sequences.\n",
    "(a) 1,2,3,4,5\n",
    "\n",
    "(b) 5,4,3,2,1\n",
    "\n",
    "(c) 5,10,15,20,25,30 \n",
    "\n",
    "(d) 30,25,20,15,10,5 \n",
    "\n",
    "(e) Empty sequence"
   ]
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   "source": [
    "#### Print out the message \"Hello!\" 10 times separated by spaces. "
   ]
  },
  {
   "cell_type": "code",
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   "metadata": {},
   "source": [
    "#### Write a for loop that prints out all even numbers between 1 and 24 separated by spaces. Use python's modulo (%) operator"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
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  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Write a for loop that prints out the numbers in descending order from 20 to 1 separated by spaces. "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
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  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Write a while loop to print out all multiples of 3 between 3 and 30 separated by spaces. "
   ]
  },
  {
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   "execution_count": null,
   "metadata": {
    "collapsed": true
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   "source": [
    "#### Rewrite the following code fragment so it eliminates the continue statement. Your new code’s logic should be simpler than the logic of this fragment. \n",
    "\n",
    "```python\n",
    "x = 5\n",
    "while x > 0:\n",
    "    y = int(input())\n",
    "    if y == 25:\n",
    "        continue\n",
    "    x -= 1\n",
    "    print('x =', x)\n",
    "```"
   ]
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   "source": [
    "#### Suppose we like to generate the following sequence of numbers: Given a positive starting number $n$. \n",
    "\n",
    "#### - If the current term is even, the next term is the current term divided by 2.\n",
    "#### - If the current term is odd, the next term is the $3$ times the current term plus 1.\n",
    "\n",
    "#### Generate the sequence until the sequence reaches a $1$. The famous **Collatz Conjecture** says that this sequence will always reach 1 regardless of the initial starting value.\n",
    "\n",
    "Example: \n",
    "n = 12, 6, 3, 10, 5, 16, 8, 4, 2, 1.\n",
    "\n",
    "#### Write a segment of code that ask the user to input a positive integer `n` and use a while loop that generates the Collatz sequence."
   ]
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   "source": [
    "#### Write nested loops that generate the following:\n",
    "\n",
    "a) \n",
    "\n",
    "2 2 2 2\n",
    "\n",
    "4 4 4 4\n",
    "\n",
    "6 6 6 6\n",
    "\n",
    "8 8 8 8\n",
    "\n",
    "b)\n",
    "\n",
    "1 2 3 4 5\n",
    "\n",
    "1 2 3 4\n",
    "\n",
    "1 2 3\n",
    "\n",
    "1 2 \n",
    "\n",
    "1\n",
    "\n"
   ]
  },
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  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Use the code above for generating the Collatz sequence and write a segment of code that prints out the Collatz sequence for each number from 1-10."
   ]
  },
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   "cell_type": "code",
   "execution_count": null,
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