$arr = @(15,16,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,68,69,70,71,107,108,109,110,111,112,113)

$groups = (New-Object -TypeName "System.Collections.ArrayList")

$len = $arr.Length
$group = (New-Object -TypeName "System.Collections.ArrayList")
$group.Add($arr[0]) | Out-Null
for($i = 1; $i -lt $len; $i++) {
    if (($arr[$i] - $arr[$i-1]) -eq 1) {
        $group.Add($arr[$i]) | Out-Null
    } else {
        $groups.Add($group) | Out-Null
        $group = (New-Object -TypeName "System.Collections.ArrayList")
        $group.Add($arr[$i]) | Out-Null
    }
}
$groups.Add($group) | Out-Null

return $groups