# Factorials everywhere!

## Weekly challenge 153

Two relatively straight forward tasks this week. Solutions are in Python only as a result.

## TASK #1 › Left Factorials

Write a script to compute Left Factorials of 1 to 10. Please refer OEIS A003422 for more information.

### My solution

So after reading the linked OEIS page, I was really confused. However we can look at the solution to find a straight forward pattern, the difference between the digits is the factorials, that is `S(n) = S(n-1) + (n-1)!`. The OEIS list starts the list at 0, but the expected output starts at 1.

### Example

``````\$ ./ch-1.py
1, 2, 4, 10, 34, 154, 874, 5914, 46234, 409114
``````

You are given an integer `\$n`.

Write a script to figure out if the given integer is factorion. A factorion is a natural number that equals the sum of the factorials of its digits.

## My solution

For this task, we start with `n` as a string. I then use `num` as the integer representation, checking that the value is not a negative. Then it is a matter of using `sum(math.factorial(int(x)) for x in n)` to compute the sum of all factorials of the digits/ Finally compare that figure with `num` and print `1` if they are the same or `0` otherwise.

### Examples

``````\$ ./ch-2.py 145
1

\$ ./ch-2.py 123
0
``````