This function appears in the denominator in the general formula for each term of a Maclaurin series.
The Lah numbers relate the "rising" and "falling" types of this operation. The series of the reciprocals of this operation applied to every natural number converges to e. This function can be approximated at large numbers by the Stirling approximation. This function appears in the denominator in the general formula for each term of a Maclaurin series. This function is shifted to the right by 1 and extended to all real and complex numbers by the gamma function. This function of n gives the number of possible permutations of n objects. For 10 points, name this mathematical operation, equal to the product of all numbers from 1 to a given integer.
The Lah numbers relate the "rising" and "falling" types of this operation.
factorial