I have two problems which are based on the sequence $A007376$.
- Natural numbers starting with $1$ are written one after another like $123456789101112131415\cdots$, how could we find the $10^4$th digit from left?
- A hundred digit number is formed by writing the first $x$ natural numbers one after another as $123456789101112131415\cdots$, how to find the remainder when this number is divided by $8$?
The OEIS doesn't provide any formula that could be implemented into a under a minute solution,as this is a quantitative aptitude problem, I was wondering which is the fastest way to approach?