The Recurrence Relation obtained during application of the Frobenius Method of solving a second-order ordinary differential equation. The indicial equation (also called the Characteristic Equation) is obtained by noting that, by definition, the lowest order term (that corresponding to ) must have a Coefficient of zero. For an example of the construction of an indicial equation, see Bessel Differential Equation.
References
Morse, P. M. and Feshbach, H. Methods of Theoretical Physics, Part I. New York:
McGraw-Hill, pp. 532-534, 1953.