Pagination handlebars helper

I've build a handlebars helper that takes n total pages and currentPage and returns the HTML for the page number links, skipping out pages far away from the current page to avoid it being too big. I feel like there are a lot of if statements in there and it could be a bit more compact.

'use strict';

var config = require('config');
var pagesInGroup = config.pagesInGroup;

module.exports =  function(n, currentPage, block) {
    var accum = '';
    var preEllipsis = '';
    var postEllipsis = '';
    currentPage = parseInt(currentPage, 10);
    n = parseInt(n, 10);

    if (currentPage > (pagesInGroup / 2) + 1) {
        preEllipsis = '<li><a>...</a></li>';
    }
    if (currentPage < n - (pagesInGroup / 2)) {
        postEllipsis = '<li><a>...</a></li>';
    }

    if (currentPage === 1) {
        accum += '<li class="active"><a href="?page=1">1</a></li>'+preEllipsis;
    } else {
        accum += '<li><a href="?page=1">1</a></li>'+preEllipsis;
    }

    for(var page = 2; page < n; page++) {
        if (page !== currentPage && page <= currentPage + (pagesInGroup / 2) && page >= currentPage - (pagesInGroup / 2)) {
          accum += '<li><a href="?page='+page+'">'+page+'</a></li>';
        } else if (page === currentPage) {
          accum += '<li class="active"><a href="?page='+page+'">'+page+'</a></li>';
        }
    }

    if (n === currentPage && n>1) {
        accum += postEllipsis+'<li class="active"><a href="?page='+n+'">'+n+'</a></li>';
    } else if (n>1) {
        accum += postEllipsis+'<li><a href="?page='+n+'">'+n+'</a></li>';
    }

    return accum;
};