The following code will pull entity information, using the Metadata service, using javascript.  This code is useful for pulling the objecttypecode dynamically when they may differ between environments.

var _sWebServicesNamespace = "http://schemas.microsoft.com/crm/2006/WebServices";

function _RemoteMetaCommand(sCommand, sAction)
{
var xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
xmlhttp.open("POST", "/mscrmservices/2006/metadataservice.asmx" , false);
xmlhttp.setRequestHeader("Content-Type","text/xml; charset=utf-8");
xmlhttp.setRequestHeader("SOAPAction", _sWebServicesNamespace + "/" + sAction);

var soapmessage = "<?xml version='1.0' encoding='utf-8'?>"
soapmessage += "<soap:Envelope xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xmlns:xsd='http://www.w3.org/2001/XMLSchema' xmlns:soap='http://schemas.xmlsoap.org/soap/envelope/'>"
soapmessage += "<soap:Body>" + sCommand + "</soap:Body></soap:Envelope>"
xmlhttp.send(soapmessage);

return xmlhttp.responseXML;
}

var entity = "new_country"
var query = "<RetrieveEntityMetadata xmlns='http://schemas.microsoft.com/crm/2006/WebServices'>"
query += "<entityName>" + entity + "</entityName><flags>EntityOnly</flags></RetrieveEntityMetadata>"

//Get ObjectTypeCode

var result = _RemoteMetaCommand(query, "RetrieveEntityMetadata").selectSingleNode("//ObjectTypeCode");

var countryentitytypecode = result.text;

Here is the response.