List of mathematical constants
A mathematical constant is a key number whose value is fixed by an unambiguous definition, often referred to by a symbol (e.g., an alphabet letter), or by mathematicians' names to facilitate using it across multiple mathematical problems. For example, the constant π may be defined as the ratio of the length of a circle's circumference to its diameter. The following list includes a decimal expansion and set containing each number, ordered by year of discovery. The column headings may be clicked to sort the table alphabetically, by decimal value, or by set. Explanations of the  symbols in the right hand column can be found by clicking on them. List. </math> formula_19 where "p" is the "k" prime number formula_28where "p" is the "k" prime number where "t" is the "k" term of the Thue–Morse sequence Foias constant is the unique real number such that if "x" = "α" then the sequence diverges to infinity Mathematical constants sorted by their representations as continued fractions. The following list includes the continued fractions of some constants and is sorted by their representations. Continued fractions with more than 20 known terms have been truncated, with an  ellipsis to show that they continue. Rational numbers have two continued fractions; the version in this list is the shorter one. Decimal representations are rounded or padded to 10 places if the values are known.