Conditionally including a php file in the template

Hi.
I need to load an ad at certain intervals on index pages, and I’m trying this code:

<?php /* Start the Loop */ ?>
<?php $count = 0 ; /* Setting count to zero for ads interval */ ?>
<?php while ( have_posts() ) : the_post(); ?>
	<?php get_template_part( 'content', get_post_format() ); ?>
	<?php /* Getting the minibanner ad at certain intervals along the list of entries down the page */
	$count= $count+1;
	if($count(array('1', '5', '10', '15', true))) { include("ads/minibanner.php") ; } ; ?>
<?php endwhile; ?>

This gives me a “Fatal error: Function name must be a string in /mounted-storage/…” and so on, indicating line 33 which is this line:

if($count(array('1', '5', '10', '15', true))) { include("ads/minibanner.php") ; } ; ?>

This is in the twentyeleven theme, slightly modified but have left the functions.php file alone so far.

Any pointers?