Umbraco dynamic sitemap .cshtml template view. Based on article and gist by Alex Lindgren: https://gist.github.com/alindgren/1439022194a472d83ddf with a few tweaks for Articulate Blog Posts, https and extra Sitemap protocol entries.

gistfile1.txt

@inherits Umbraco.Web.Mvc.UmbracoTemplatePage
@using System.Linq;
@{
    Layout = null;
    Response.ContentType = "text/xml";
}<?xml version='1.0' encoding='UTF-8' ?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd">
    @ListChildNodes(Umbraco.TypedContent(UmbracoContext.Current.PageId).AncestorOrSelf(1))
</urlset>

@helper ListChildNodes(IPublishedContent startNode)
{

    <url>
        <loc>http://www.yourlandingpage.com/</loc>
        <lastmod>@(string.Format("{0:s}+00:00", startNode.UpdateDate))</lastmod>
        <changefreq>weekly</changefreq>
        <priority>1.0</priority>
    </url>

    foreach (var node in startNode.Children.Where("hideInXmlSitemap == false"))
    {
        if (node.TemplateId > 0 || node.DocumentTypeAlias == "ArticulateMarkdown" || node.DocumentTypeAlias == "ArticulateRichText")
        {
                <url>
                    <loc>@GetUrlWithDomainPrefix(node.Url)</loc>
                    <lastmod>@(string.Format("{0:s}+00:00", node.UpdateDate))</lastmod>
                    <priority>0.4</priority>
                    <changefreq>monthly</changefreq>
                </url>
            }

        if (node.Level <= 100 && node.Children.Count() > 0)
        {
            @ListChildNodes(node)
            }
    }
}

@functions {
    private static string GetUrlWithDomainPrefix(string url)
    {
        if (url.StartsWith("/"))
            url = url.Substring(1);

        var domainPrefix = string.Format("https://{0}/", HttpContext.Current.Request.ServerVariables["HTTP_HOST"]);

        if (url.StartsWith(domainPrefix))
            return url;
        else
            return domainPrefix + url;
    }
}