67 lines
1.2 KiB
Markdown
67 lines
1.2 KiB
Markdown
|
---
|
||
|
|
id: 5900f3911000cf542c50fea4
|
||
|
|
title: 'Problem 37: Truncatable primes'
|
||
|
|
challengeType: 5
|
||
|
|
forumTopicId: 302031
|
||
|
|
dashedName: problem-37-truncatable-primes
|
||
|
|
---
|
||
|
|
|
||
|
|
# --description--
|
||
|
|
|
||
|
|
The number 3797 has an interesting property. Being prime itself, it is possible to continuously remove digits from left to right, and remain prime at each stage: 3797, 797, 97, and 7. Similarly we can work from right to left: 3797, 379, 37, and 3.
|
||
|
|
|
||
|
|
Find the sum of the only `n` (8 ≤ `n` ≤ 11) primes that are both truncatable from left to right and right to left.
|
||
|
|
|
||
|
|
NOTE: 2, 3, 5, and 7 are not considered to be truncatable primes.
|
||
|
|
|
||
|
|
# --hints--
|
||
|
|
|
||
|
|
`truncatablePrimes(8)` should return a number.
|
||
|
|
|
||
|
|
```js
|
||
|
|
assert(typeof truncatablePrimes(8) === 'number');
|
||
|
|
```
|
||
|
|
|
||
|
|
`truncatablePrimes(8)` should return 1986.
|
||
|
|
|
||
|
|
```js
|
||
|
|
assert(truncatablePrimes(8) == 1986);
|
||
|
|
```
|
||
|
|
|
||
|
|
`truncatablePrimes(9)` should return 5123.
|
||
|
|
|
||
|
|
```js
|
||
|
|
assert(truncatablePrimes(9) == 5123);
|
||
|
|
```
|
||
|
|
|
||
|
|
`truncatablePrimes(10)` should return 8920.
|
||
|
|
|
||
|
|
```js
|
||
|
|
assert(truncatablePrimes(10) == 8920);
|
||
|
|
```
|
||
|
|
|
||
|
|
`truncatablePrimes(11)` should return 748317.
|
||
|
|
|
||
|
|
```js
|
||
|
|
assert(truncatablePrimes(11) == 748317);
|
||
|
|
```
|
||
|
|
|
||
|
|
# --seed--
|
||
|
|
|
||
|
|
## --seed-contents--
|
||
|
|
|
||
|
|
```js
|
||
|
|
function truncatablePrimes(n) {
|
||
|
|
|
||
|
|
return n;
|
||
|
|
}
|
||
|
|
|
||
|
|
truncatablePrimes(11);
|
||
|
|
```
|
||
|
|
|
||
|
|
# --solutions--
|
||
|
|
|
||
|
|
```js
|
||
|
|
// solution required
|
||
|
|
```
|