Base 4 has 2 possible final digits
At 1 digits, there were 2 primes, 0 leaders
At 2 digits, there were 2 primes, 0 leaders
At 3 digits, there were 2 primes, 1 leaders
At 4 digits, there were 1 primes, 1 leaders
In total, in base 4 there were 7 primes and 2 leaders, maxlen=4