> 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/l/lucas-lehmer_test.md).

# Lucas-Lehmer test

```ruby
func is_mersenne_prime(p) {
    return true if (p == 2)
    var s = 4
    var M = (2**p - 1)
    { s = powmod(s, 2, M)-2 } * (p-2)
    s == 0
}

Inf.times {|n|
    if (n.is_prime && is_mersenne_prime(n)) {
        say "M#{n}"
    }
}
```

#### Output:

```
M2
M3
M5
M7
M13
M17
M19
M31
M61
M89
M107
M127
M521
M607
M1279
M2203
M2281
^C
```