::: spoiler spoiler solution: https://gmtex.siri.sh/fs/1/School/Extra/Maths/Qotd%20solutions/2024-06-30_sizes-of-real-sets.html :::
Sure, but what is d_\infty? What is the set \infty? What does the question mean by "every real number can be represented by"? There's nothing distinguishing d_1d_2... with d_1 times d_2 since we normally denote the product by writing the variables next to each other