> For the complete documentation index, see [llms.txt](https://trizen.gitbook.io/sidef-lang/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://trizen.gitbook.io/sidef-lang/programming_tasks/g/giuga_numbers.md).

# Giuga numbers

```ruby
4..Inf `by` 2 -> lazy.grep {|n|
    n.factor.all {|p| p `divides` (n/p - 1) }
}.first(4).say
```

#### Output:

```
[30, 858, 1722, 66198]
```