PHP script to display the last 20 post in wordpress blog

Need a simple php script to display the last 20 wordpress blog posts from specified wordpress category on the static home page. Basically this script will be added to wordpress template file called [login to view URL] and performs simple conditional check to see if the loaded page is the home page and if it is then it displays the last 20 posts titles (non hyperlinked) from a category that I specify in the script. Each title is followed by 400 character of the post content, also if there is an image in the post then under the title it displays a thumbnail, also it follow again with the title but this time it is hyperlinked back to the post. The script does this for each post that is part of the last 20 posts.