AABAABCAABAABCD

by serGlazkov

JavaScript

// AABAABCAABAABCD
const alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';

let n = 10000;

const logIt = p => Math.floor(Math.log(p + 1) / Math.log(2));

let i = logIt(n);
while (true) {
  console.log('i', i);
  let pow = Math.pow(2, i) - 1;
  if (pow === n) {
    break;
  }
  if (n > pow && n <= pow * 2) {
    n = n - pow;
    i = logIt(n);
  }
}
console.log('find', n);

console.log('symbol', alphabet[i - 1]);