A number with a continued fraction whose terms are the values of one or more polynomials evaluated on consecutive integers and then interleaved. This property is preserved by Möbius transformations (Gosper 1972, p. 44).
Hurwitz Number
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References
Gosper, R. W. Item 101b in Beeler, M.; Gosper, R. W.; and Schroeppel, R. HAKMEM. Cambridge, MA: MIT Artificial Intelligence Laboratory, Memo AIM-239, pp. 39-44, Feb. 1972. http://www.inwap.com/pdp10/hbaker/hakmem/cf.html#item101b.Referenced on Wolfram|Alpha
Hurwitz NumberCite this as:
Weisstein, Eric W. "Hurwitz Number." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/HurwitzNumber.html