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curriculum/challenges/english/10-coding-interview-prep/project-euler/problem-230-fibonacci-words.md

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+---
+id: 5900f4531000cf542c50ff65
+challengeType: 5
+title: 'Problem 230: Fibonacci Words'
+forumTopicId: 301874
+---
+
+## Description
+<section id='description'>
+For any two strings of digits, A and B, we define FA,B to be the sequence (A,B,AB,BAB,ABBAB,...) in which each term is the concatenation of the previous two.
+
+Further, we define DA,B(n) to be the nth digit in the first term of FA,B that contains at least n digits.
+
+Example:
+
+Let A=1415926535, B=8979323846. We wish to find DA,B(35), say.
+
+The first few terms of FA,B are:
+1415926535
+8979323846
+14159265358979323846
+897932384614159265358979323846
+14159265358979323846897932384614159265358979323846
+
+Then DA,B(35) is the 35th digit in the fifth term, which is 9.
+
+Now we use for A the first 100 digits of π behind the decimal point:
+14159265358979323846264338327950288419716939937510
+58209749445923078164062862089986280348253421170679
+
+and for B the next hundred digits:
+
+82148086513282306647093844609550582231725359408128
+48111745028410270193852110555964462294895493038196 .
+
+Find ∑n = 0,1,...,17   10n× DA,B((127+19n)×7n) .
+</section>
+
+## Instructions
+<section id='instructions'>
+
+</section>
+
+## Tests
+<section id='tests'>
+
+```yml
+tests:
+  - text: <code>euler230()</code> should return 850481152593119200.
+    testString: assert.strictEqual(euler230(), 850481152593119200);
+
+```
+
+</section>
+
+## Challenge Seed
+<section id='challengeSeed'>
+
+<div id='js-seed'>
+
+```js
+function euler230() {
+
+  return true;
+}
+
+euler230();
+```
+
+</div>
+
+
+
+</section>
+
+## Solution
+<section id='solution'>
+
+```js
+// solution required
+```
+
+</section>