Compute
\[\sum_{1 \le j < i} \frac{1}{2^{i + j}},\]where the sum is taken over all positive integers $i$ and $j$ such that $1 \le j < i.$
Question:
Compute
\[\sum_{1 \le j < i} \frac{1}{2^{i + j}},\]where the sum is taken over all positive integers $i$ and $j$ such that $1 \le j < i.$
Answer:
Let's think step by step.

user
\frac{1}{3}
Compute
\[\sum_{1 \le j < i} \frac{1}{2^{i + j}},\]where the sum is taken over all positive integers $i$ and $j$ such that $1 \le j < i.$
train