Connecting SharePoint 2013 External List to Outlook 2013
The steps haven't changed since SharePoint 2010, so I am not going to bore you with how to create an External List that will Sync with Outlook, but something to keep in mind while configuring this, you need to manually enable a feature in SharePoint 2013 before you can do a Sync with Outlook 2013. Go to Site Feature and Enable: Offline Synchronization for Offline Lists
Other software that your machine might need for the Sync to work are listed here: https://office.microsoft.com/en-us/sharepoint-help/prerequisite-software-needed-to-work-with-external-data-in-office-2013-HA102846750.aspx
Cheers!
Priyo