An arithmetic progression is simply a sequence of numbers that are all separated by the same amount. For example, 6, 8, 10, 12, 14, 16 is an arithmetic progression, where the difference is 2.
"Many things we find beautiful are so because they are very symmetric, reducing the work we need to understand them," says Benjamin Doyon of King's College London in the UK. "Perhaps our brain is simply happy to have to do less work, creating a positive feeling of beauty."
This concept of "algorithmic reduction" permeates all of science, says Doyon. He says that he personally finds any algorithmic reduction to be beautiful.
"When you've reduced the number of operations you have to do, you really understand what is going on," says Doyon.
Read more: What is the most beautiful equation?