The triangle coefficient is function of three variables written 
and defined by
 |
(Shore and Menzel 1968, p. 273), where 
is a factorial. It arises for example in the definition of the Wigner 6j-symbol.
Triangle Coefficient
See also
Wigner 6j-SymbolExplore with Wolfram|Alpha
References
Messiah, A. Quantum Mechanics, Vol. 2. Amsterdam, Netherlands: North-Holland, p. 1058, 1962.Shore, B. W. and Menzel, D. H. Principles of Atomic Spectra. New York: Wiley, 1968.Referenced on Wolfram|Alpha
Triangle CoefficientCite this as:
Weisstein, Eric W. "Triangle Coefficient." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/TriangleCoefficient.html