@PypeBros@mastodon.social It always holds, for any n! The sum of cubes from 1³ to n³ can be expressed as n²(n+1)²/4. This is the same as (n(n+1)/2)². The sum of the first n positive integers is expressed as n(n+1)/2 (n numbers times the average of first and last, (n+1)/2. So, if you square the last expression, you get the other expression. ☐