How can I get a custom number of posts on the front page without views?
The default front page article count is on the Site Information admin page @ admin/config/system/site-information. For some reason you can't select 16 as a value. If you have drush you can manually set the default_nodes_main value:

drush vset default_nodes_main 16


If you don't have drush you can set its value in the variables table.