Square root of 5
2.23606797749978969640917366873127623544061835961152572427089… (sequence A002163 in the OEIS). which can be rounded down to 2.236 to within 99.99% accuracy. The approximation 161/72 (≈ 2.23611) for the square root of five can be used. Despite having a denominator of only 72, it differs from the correct value by less than 1/10,000 (approx. 4.3×10−5). As of November 2019, its numerical value in decimal has been computed to at least 2,000,000,000,000 digits.
Square root of 5-3