I'm not sure I understand the prime density thing. Of the numbers up to 8258, about 12.5% are prime. Accounting for the fact that about a quarter of these primes ends in 101, i.e. cannot occur, I would expect about 10.7% = 12.5% * (3/4) / (7/8), which is fairly close to the observed 9.4%.
The 2.1% in the README seems to be the density of primes < 1000 among numbers up to 8258. That's not what was counted.
The 2.1% in the README seems to be the density of primes < 1000 among numbers up to 8258. That's not what was counted.