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freeCodeCamp/curriculum/challenges/english/10-coding-interview-prep/project-euler/problem-229-four-representations-using-squares.md
gikf a9418a1fe9 fix(curriculum): clean-up Project Euler 221-240 (#42839)
* fix: clean-up Project Euler 221-240

* fix: corrections from review

Co-authored-by: Tom <20648924+moT01@users.noreply.github.com>

Co-authored-by: Tom <20648924+moT01@users.noreply.github.com>
2021-07-15 14:26:34 +02:00

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id, title, challengeType, forumTopicId, dashedName
id title challengeType forumTopicId dashedName
5900f4521000cf542c50ff64 Problem 229: Four Representations using Squares 5 301872 problem-229-four-representations-using-squares

--description--

Consider the number 3600. It is very special, because

$$\begin{align} & 3600 = {48}^2 + {36}^2 \\ & 3600 = {20}^2 + {2×40}^2 \\ & 3600 = {30}^2 + {3×30}^2 \\ & 3600 = {45}^2 + {7×15}^2 \\ \end{align}$$

Similarly, we find that 88201 = {99}^2 + {280}^2 = {287}^2 + 2 × {54}^2 = {283}^2 + 3 × {52}^2 = {197}^2 + 7 × {84}^2.

In 1747, Euler proved which numbers are representable as a sum of two squares. We are interested in the numbers n which admit representations of all of the following four types:

$$\begin{align} & n = {a_1}^2 + {b_1}^2 \\ & n = {a_2}^2 + 2{b_2}^2 \\ & n = {a_3}^2 + 3{b_3}^2 \\ & n = {a_7}^2 + 7{b_7}^2 \\ \end{align}$$

where the a_k and b_k are positive integers.

There are 75373 such numbers that do not exceed {10}^7.

How many such numbers are there that do not exceed 2 × {10}^9?

--hints--

representationsUsingSquares() should return 11325263.

assert.strictEqual(representationsUsingSquares(), 11325263);

--seed--

--seed-contents--

function representationsUsingSquares() {

  return true;
}

representationsUsingSquares();

--solutions--

// solution required