I am interested in generating a bitcoin address with the shortest possible FirstBits. By random trial and error I found that 1ijj1 is untaken. Is there a way to find the shortest possible untaken FirstBits? (So I can generate it using vanitygen)
Yes there is a solution, it is brute-force. Make a loop and add variable characters, test them one by one. Start with one variable characters, try all combinations, add another variable character, try all combinations, rinse, repeat until you find unused firstbits.