website.com/leaders/page/[page_number]

$this->load->library('pagination');

    $config['per_page'] = $query_config['limit'];
    $config['base_url'] = base_url() . 'leaders/page/';
    $config['total_rows'] = 2000; // I actually use a function for this number
    $config['full_tag_open'] = '<div id="paginate">';
    $config['full_tag_close'] = '</div>';
    $config['first_link'] = '&laquo; First';
    $config['last_link'] = 'Last &raquo;';
    $config['use_page_numbers'] = true;
    $config['uri_segment'] = 3;

    $this->pagination->initialize($config);

website.com/leaders/page/2

$route['leaders/page/(:num)'] = 'leaders/index';
$route['leaders/page'] = 'leaders/index';

$config['base_url'] = base_url . 'leaders/index';

public function index($page=''){
    //...
    $page = ($page!='')? $page : 0;
    $config["cur_page"] = $page;

    //...

}

if ($this->uri->segment(3) > 0) {
     $offset = $this->uri->segment(3) * $config['per_page'] - $config['per_page'];
 } else {
     $offset = $this->uri->segment(3);
 }

$config['base_url'] = base_url().'Cseguimiento/buscar_reportes/';
$config['uri_segment'] = 3;
$config['use_page_numbers'] = TRUE;
$config['first_link'] = FALSE;
$config['last_link'] = FALSE;
$config['next_link'] = '>';
$config['prev_link'] = '<';
$config["full_tag_open"] = '<ul class="pagination">';
$config["full_tag_close"] = '</ul>';
$config["first_tag_open"] = '<li>';
$config["first_tag_close"] = '</li>';
$config["last_tag_open"] = '<li>';
$config["last_tag_close"] = '</li>';
$config["next_tag_open"] = '<li>';
$config["next_tag_close"] = '</li>';
$config["prev_tag_open"] = "<li>";
$config["prev_tag_close"] = "</li>";
$config["cur_tag_open"] = "<li>";
$config["cur_tag_close"] = "</li>";
$config["num_tag_open"] = "<li>";
$config["num_tag_close"] = "</li>";
$config['total_rows'] = $this->mseguimiento->filas($fecha_inicio,$fecha_fin);
$config['per_page'] = 10;
$choice = $config["total_rows"] / $config["per_page"];
$config["num_links"] = round($choice);
$page = $config['uri_segment'] * $config['per_page'];
$this->pagination->initialize($config);
$offset = ($this->uri->segment(3)-1)*$config['per_page'];
$output = array(
    'pagination_link'  => $this->pagination->create_links(),
    'lista_reportes'   => $this->mseguimiento->fetch_details($this->pagination->per_page, $offset,$fecha_inicio,$fecha_fin)
    );