Levenshtein distance & OEIS (Cops)
Haskell, LD = 13, cracked



((snd.span(&lt;'1').reverse.show.(^2)=&lt;&lt;[1..])!!)


Try it online! 

I double-checked that leading zeros are trimmed ;)

Explanation:

                    [1..]     -- for each element in [1,2,3,4,5,...]
                 =&lt;&lt;          -- apply the following functions 
             (^2)             -- square [1,4,9,16,25,...]
           show.              -- convert to string ["1","4","9","16","25",...]
       reverse.               -- reverse ["1","4","9","61","52",...,"001",...]
   span(&lt;'1').                -- split into leading zeros and remainder [("","1"),("","4"),...,("00","1"),...]
  snd.                        -- only keep remainder ["1","4","9","61","52",...,"1",...]
                              -- and concatenate the result "1496152..."
((                       )!!) -- index into the sequence