## Constant

Any Real Number which is significant'' (or interesting) in some way. In this work, the term constant'' is generally reserved for Real nonintegral numbers of interest, while Number'' is reserved for interesting Integers (e.g., Brun's Constant, but Beast Number).

Certain constants are known to many Decimal Digits and recur throughout many diverse areas of mathematics, often in unexpected and surprising places (e.g., Pi, e, and to some extent, the Euler-Mascheroni Constant ). Other constants are more specialized and may be known to only a few Digits. S. Plouffe maintains a site about the computation and identification of numerical constants. Plouffe's site also contains a page giving the largest number of Digits computed for the most common constants. S. Finch maintains a delightful, more expository site containing detailed essays and references on constants both common and obscure.

See also Abundant Number, Alladi-Grinstead Constant, Apéry's Constant, Archimedes' Constant, Artin's Constant, Backhouse's Constant, Beraha Constants, Bernstein's Constant, Bloch Constant, Brun's Constant, Cameron's Sum-Free Set Constant, Carlson-Levin Constant, Catalan's Constant, Chaitin's Constant, Champernowne Constant, Chebyshev Constants, Chebyshev-Sylvester Constant, Comma of Didymus, Comma of Pythagoras, Conic Constant, Constant Function, Constant Problem, Continued Fraction Constant, Conway's Constant, Copeland-Erdos Constant, Copson-de Bruijn Constant, de Bruijn-Newman Constant, Delian Constant, Diesis, Du Bois Raymond Constants, e, Ellison-Mendès-France Constant, Erdös Reciprocal Sum Constants, Euler-Mascheroni Constant, Extreme Value Distribution, Favard Constants, Feller's Coin-Tossing Constants, Fransén-Robinson Constant, Freiman's Constant, Gauss's Circle Problem, Gauss's Constant, Gauss-Kuzmin-Wirsing Constant, Gelfond-Schneider Constant, Geometric Probability Constants, Gibbs Constant, Glaisher-Kinkelin Constant, Golden Mean, Golomb Constant, Golomb-Dickman Constant, Gompertz Constant, Grossman's Constant, Grothendieck's Constant, Hadamard-Vallée Poussin Constants, Hafner-Sarnak-McCurley Constant, Halphen Constant, Hard Square Entropy Constant, Hardy-Littlewood Constants, Hermite Constants, Hilbert's Constants, Infinite Product, Iterated Exponential Constants, Khintchine's Constant, Khintchine-Lévy Constant, Koebe's Constant, Kolmogorov Constant, Lal's Constant, Landau Constant, Landau-Kolmogorov Constants, Landau-Ramanujan Constant, Lebesgue Constants (Fourier Series), Lebesgue Constants (Lagrange Interpolation), Legendre's Constant, Lehmer's Constant, Lengyel's Constant, Lévy Constant, Linnik's Constant, Liouville's Constant, Liouville-Roth Constant, Ludolph's Constant, Madelung Constants, Magic Constant, Magic Geometric Constants, Masser-Gramain Constant, Mertens Constant, Mills' Constant, Moving Sofa Constant, Napier's Constant, Nielsen-Ramanujan Constants, Niven's Constant, Omega Constant, One-Ninth Constant, Otter's Tree Enumeration Constants, Parity Constant, Pi, Pisot-Vijayaraghavan Constants, Plastic Constant, Plouffe's Constant, Polygon Circumscribing Constant, Polygon Inscribing Constant, Porter's Constant, Pythagoras's Constant, Quadratic Recurrence, Quadtree, Rabbit Constant, Ramanujan Constant, Random Walk, Rényi's Parking Constants, Robbin Constant, Salem Constants, Self-Avoiding Walk, Shah-Wilson Constant, Shallit Constant, Shapiro's Cyclic Sum Constant, Sierpinski Constant, Silver Constant, Silverman Constant, Smarandache Constants, Soldner's Constant, Sphere Packing, Stieltjes Constants, Stolarsky-Harborth Constant, Sylvester's Sequence, Thue Constant, Thue-Morse Constant, Totient Function Constants, Traveling Salesman Constants, Tree Searching, Twin Primes Constant, Varga's Constant, W2-Constant, Weierstraß Constant, Whitney-Mikhlin Extension Constants, Wilbraham-Gibbs Constant, Wirtinger-Sobolev Isoperimetric Constants

References

Borwein, J. and Borwein, P. A Dictionary of Real Numbers. London: Chapman & Hall, 1990.

Finch, S. Favorite Mathematical Constants.'' http://www.mathsoft.com/asolve/constant/constant.html.

Le Lionnais, F. Les nombres remarquables. Paris: Hermann, 1983.

Plouffe, S. Inverse Symbolic Calculator Table of Constants.'' http://www.cecm.sfu.ca/projects/ISC/I_d.html.

Plouffe, S. Plouffe's Inverter.'' http://www.lacim.uqam.ca/pi/.

Plouffe, S. Plouffe's Inverter: Table of Current Records for the Computation of Constants.'' http://www.lacim.uqam.ca/pi/records.html.

Wells, D. W. The Penguin Dictionary of Curious and Interesting Numbers. Harmondsworth, England: Penguin Books, 1986.