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## Discussion of Problem 2061. OEIS A216264

Some Deductions on the Problem
Posted by orzczt 3 Apr 2016 12:54
If you search for the id "A216264" on oeis.org, you would find a table of a(n), n=1..60.
One interesting thing is that the site said that it was Mikhail Rubinchik who calculated a(26) to a(60), which happened to be out of the brute-force range. What is really disappointing is that in this problem, n may be 61, I think it's that guys's trick to play with us. Another interesting fact is that this guy also invented and introduced the Palindromic Tree. So, I deduce that the solution to this problem is somehow related to this data structure.

Edited by author 03.04.2016 12:56
Re: Some Deductions on the Problem
Posted by Vit Demidenko 20 Nov 2018 17:16
Yes, with eertree you can bruteforce all answers
My solution runs ~20 hours to generate result, it can be theoretically speed up 2 times by bruteforcing only strings such s<=reverse(s)
Re: Some Deductions on the Problem
Posted by Levon Oganesyan 3 Mar 2020 03:05
How could you bruteforce 2^61 strings of length 61?
Re: Some Deductions on the Problem
Posted by Virus TI 27 Jun 2020 01:37
imagine a binary tree of these strings, use DFS with eertree