Added 24 and 25 to ipython.

ipython/EulerProblem025.ipynb

@@ -0,0 +1,100 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Euler Problem 25\n",
+    "\n",
+    "The Fibonacci sequence is defined by the recurrence relation:\n",
+    "\n",
+    "$F_n = F_{n−1} + F_{n−2}$, where $F_1 = 1$ and $F_2 = 1$.\n",
+    "Hence the first 12 terms will be:\n",
+    "\n",
+    "~~~\n",
+    "F1 = 1\n",
+    "F2 = 1\n",
+    "F3 = 2\n",
+    "F4 = 3\n",
+    "F5 = 5\n",
+    "F6 = 8\n",
+    "F7 = 13\n",
+    "F8 = 21\n",
+    "F9 = 34\n",
+    "F10 = 55\n",
+    "F11 = 89\n",
+    "F12 = 144\n",
+    "~~~\n",
+    "\n",
+    "The 12th term, $F_{12}$, is the first term to contain three digits.\n",
+    "\n",
+    "What is the index of the first term in the Fibonacci sequence to contain 1000 digits?"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Reuse fibonacci generator and then straight forward."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "4782\n"
+     ]
+    }
+   ],
+   "source": [
+    "def fibonacci_generator():\n",
+    "    a = 0\n",
+    "    b = 1\n",
+    "    yield 1\n",
+    "    while True:\n",
+    "        yield a + b\n",
+    "        a, b = b, (a + b)\n",
+    "        \n",
+    "for i, f in enumerate(fibonacci_generator()):\n",
+    "    if len(str(f)) >= 1000:\n",
+    "        break\n",
+    "\n",
+    "s = i + 1\n",
+    "assert(s == 4782)\n",
+    "print(s)"
+   ]
+  }
+ ],
+ "metadata": {
+  "completion_date": "Fri, 5 Sep 2014, 14:57",
+  "kernelspec": {
+   "display_name": "Python 3",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.5.4"
+  },
+  "tags": [
+   "fibonacci"
+  ]
+ },
+ "nbformat": 4,
+ "nbformat_minor": 0
+}