Add Widget Middle of Archives Page.php

<?php
//* Do NOT include php tag

// register sidebar for the middle of the posts in home or archive page
genesis_register_sidebar( array(
        'id'          => 'sidebar-somewhere-in-the-posts',
        'name'        => __( 'Middle of Posts Widget Area' ),
        'description' => __( 'Display widgets in the middle of your posts on the home or archive pages.' ),
) );

add_action( 'genesis_before_post', 'display_somewhere_in_posts_sidebar' );
add_action( 'genesis_before_entry', 'display_somewhere_in_posts_sidebar' );
/**
 * Callback for Genesis Framework 'genesis_before_post' or 'genesis_before_entry' action.
 * 
 * Display widget area on home page or archive pages within the middle of the posts.
 * 
 * @author Ryan Meier http://www.rfmeier.net/
 * 
 * @global object $wp_query the WP_Query object
 * @return null exit
 */
function display_somewhere_in_posts_sidebar(){
        
        // if home page or archive page...
        if( is_archive() ){
                
                global $wp_query;
                global $posts;
                
                // check for valid current_post (index)
                if( ! isset( $wp_query->current_post ) )
                        return;
                
                // get posts per page
                $posts_per_page = (int) get_option( 'posts_per_page' );
                
                // if empty posts per page, return
                if( empty( $posts_per_page ) )
                        return;
                
                // if not a full page of posts, return
                if( count( $posts ) < $posts_per_page )
                        return;
                
                // determine the middle-ish index
                $middle_index = intval( ceil( $posts_per_page / 2 ) );
                
                // if invalid middle index, return
                if( empty( $middle_index ) )
                        return;
                
                // if the middle-ish index post ID is NOT the current post ID, return
                if( $middle_index != $wp_query->current_post )
                        return;
                
                // display the widget area
                genesis_widget_area( 'sidebar-somewhere-in-the-posts' );
                
        }
        
}