RewriteEngine On
RewriteCond %{HTTP_HOST} ^yourdomain\.com$ [NC]
RewriteRule ^(.*)$ http://www.yourdomain.com%{REQUEST_URI} [R=301,L]

RewriteBase /

RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /([^/]+/)*index\.(html|php)\ HTTP/
RewriteRule ^(([^/]+/)*)index\.(html|php)$ http://yourdomain.com/$1 [R=301,L]