data/problems/305.yml
---
:id: 305
:name: Reflexive Position
:url: https://projecteuler.net/problem=305
:content: "Let's call S the (infinite) string that is made by concatenating the consecutive
positive integers (starting from 1) written down in base 10. \n Thus, S = 1234567891011121314151617181920212223242...\n\nIt's
easy to see that any number will show up an infinite number of times in S.\n\nLet's
call f(n) the starting position of the n<sup>th</sup> occurrence of n in S. \n
For example, f(1)=1, f(5)=81, f(12)=271 and f(7780)=111111365.\n\nFind ∑f(3<sup>k</sup>)
for 1≤k≤13.\n\n"