Need help querying posts

I’m incrementing my posts and would like to display the 1st, 4th, 7th, and 10th… post –basically every third post starting with 1.

My loop example checks for and displays even numbered posts:

<?php
if (have_posts()) :
while(have_posts()) :
$i++;
if(($i % 2) == 0) : $wp_query->next_post();
else : the_post();
?>

What should this look like:
if(($i % 2) == 0)

Thank you for the help.