RewriteRule ^action.php?([0-9]*)/?$ action.php?name=&age=$1 [L,QSA]
RewriteRule ^action.php?([^/]+)/?$ action.php?name=&age=$1 [L,QSA]
RewriteRule ^action.php?1/ ?$ action.php?name=&age=$1 [L,QSA]