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add_action( 'genesis_entry_header', 'single_post_featured_image', 5 );

function single_post_featured_image() {

	if ( ! is_singular() )
		return;

	$img = genesis_get_image( array( 'format' => 'html', 'size' => genesis_get_option( 'image_size' ), 'attr' => array( 'class' => 'post-image' ) ) );
	printf( '<a href="%s" title="%s">%s</a>', get_permalink(), the_title_attribute( 'echo=0' ), $img );

}