Why this works for any starting number is left as an exercise for the interested reader.

# 1089 (idea)

See all of 1089, there is 1 more in this node.

See all of 1089, there is 1 more in this node.

Write down any three-digit number. Now write it down backwards, so you have two numbers before you. Subtract the smaller from the larger one. Take the resulting number and add it to its own reversal. The result of this addition is the title of this node.

Why this works for any starting number is left as an exercise for the interested reader.