hints

16 symbols
only uses lowercase and uppercase letters
completely random string of letters
there are 4 capital letters and 12 lowercase letters
there are 13 different letters
1 letter appears more than twice
sum of all ascii - 1627 (uppercase: 314, lowercase: 1313)
small letters are from d to u
big letters are from B to Y
rHaAaaaarArhaaaA -> other letters do not repeat (aA represents any letter)