FactorialPower[x,n]
gives the factorial power
.
FactorialPower[x,n,h]
gives the step-h factorial power
.
FactorialPower
FactorialPower[x,n]
gives the factorial power
.
FactorialPower[x,n,h]
gives the step-h factorial power
.
Details
- Mathematical function, suitable for both symbolic and numeric manipulation.
- For integer n,
is given by
, and
is given by
.
is given for any n by
.
is given by
and
is given by
.- FactorialPower[x,n] evaluates automatically only when x and n are numbers.
- FunctionExpand always converts FactorialPower to a polynomial or combination of gamma functions.
- FactorialPower can be used with Interval and CenteredInterval objects. »
Examples
open all close allBasic Examples (6)
Find the "factorial square" of 10:
FactorialPower[10, 2]FactorialPower does not automatically expand out:
FactorialPower[x, 8]Use FunctionExpand to do the expansion:
FunctionExpand[%]Plot over a subset of the reals:
Plot[FactorialPower[x, 3], {x, -3, 4}]Plot over a subset of complexes:
ComplexPlot3D[FactorialPower[z ^ 2, 5], {z, -2 - 2I, 2 + 2I}, PlotLegends -> Automatic]Series expansion at the origin:
Series[FactorialPower[x, 5], {x, 0, 5}]//FullSimplifySeries expansion at Infinity:
Series[FactorialPower[x, 5], {x, ∞, 6}]//FullSimplifyScope (35)
Numerical Evaluation (7)
FactorialPower[2, .9]FactorialPower[4, 2]N[FactorialPower[1 / 3, 7, 3], 50]The precision of the output tracks the precision of the input:
FactorialPower[0.100000000000000000, 7, 3]FactorialPower[1 + I, I, 3.]Evaluate efficiently at high precision:
FactorialPower[1 / 3, 7, 3`100]//TimingFactorialPower[2`1000, 1 / 5, 1 / 3];//TimingFactorialPower threads elementwise over lists:
FactorialPower[4, {1, 2, 3, 4, 5}]Compute worst-case guaranteed intervals using Interval and CenteredInterval objects:
FactorialPower[0.3, 0.4, Interval[{0.5, 0.6}]]FactorialPower[1 / 2, 1 / 3, CenteredInterval[1 / 5, 1 / 1000]]Or compute average-case statistical intervals using Around:
FactorialPower[Around[2, 0.01], 2]Compute the elementwise values of an array:
FactorialPower[{{1, 2}, {3, 4}}, 2]Or compute the matrix FactorialPower function using MatrixFunction:
MatrixFunction[FactorialPower[#, .2]&, {{1, 2}, {3, 4}}]Specific Values (6)
Values of FactorialPower at fixed points:
Table[FactorialPower[x, 2], {x, 1, 5}]Obtain the polynomial representation FactorialPower[x,n] for integer values of n:
FactorialPower[x, 4]//FunctionExpandWith step
, FactorialPower[x,n,h] gives the rising factorial:
FunctionExpand[FactorialPower[x, 5, -1]]This is equivalent to Pochhammer:
Pochhammer[x, 5]Expand FactorialPower[x,n] for a fixed value of x:
FactorialPower[(3/2), n]//FunctionExpandDo the same while adding integer values for the third argument:
Table[FactorialPower[(3/2), n, h], {h, 0, 3}]//FunctionExpandValue with second argument zero:
FactorialPower[n, 0]Value with first argument 0 and positive second argument:
FullSimplify[FactorialPower[0, n], n∈PositiveIntegers]//QuietFind a value of x for which FactorialPower[x,1/7]=1.2:
xval = x /. FindRoot[FactorialPower[ x , 1 / 7] == 1.2, {x, 3}]Plot[FactorialPower[x, 1 / 7], {x, 0, 10}, Epilog -> Style[Point[{xval, FactorialPower[xval, 1 / 7]}], PointSize[Large], Red]]Visualization (3)
Plot the FactorialPower function for various orders:
Plot[{FactorialPower[x, 1], FactorialPower[x, 2], FactorialPower[x, 3], FactorialPower[x, 4]}, {x, -3, 3}]Plot FactorialPower as a function of its parameter
:
Plot[{FactorialPower[1 / 2, n], FactorialPower[1, n], FactorialPower[3 / 2, n], FactorialPower[2, n]}, {n, -4, 4}, PlotLegends -> "Expressions"]ComplexContourPlot[Re[FactorialPower[z, 5]], {z, -1 - 2I, 1 + 2 I}, Contours -> 20]ComplexContourPlot[Im[FactorialPower[z, 5]], {z, -1 - 2I, 1 + 2 I}, Contours -> 20]Function Properties (10)
Real domain of the factorial power:
FunctionDomain[FactorialPower[x, y], {x, y}]FunctionDomain[FactorialPower[w, z], {w, z}, Complexes]Function range of FactorialPower[x,n] for various fixed values of n:
Table[FunctionRange[FactorialPower[x, n], x, y], {n, {0, 1 / 2, 1, 2}}]FunctionAnalytic[FactorialPower[x, 3], x]
is neither nondecreasing nor nonincreasing:
FunctionMonotonicity[FactorialPower[x, 3], x]FunctionInjective[FactorialPower[x, 3], x]Plot[{FactorialPower[x, 3], .2}, {x, -1, 3}]FunctionSurjective[FactorialPower[x, 3], x]Plot[{FactorialPower[x, 3], 10}, {x, -5, 5}]FactorialPower is neither non-negative nor non-positive:
FunctionSign[FactorialPower[x, 1], x]
has potential singularities and discontinuities when
is a negative integer:
FunctionSingularities[FactorialPower[x, y], {x, y}]FunctionDiscontinuities[FactorialPower[x, y], {x, y}]
is neither convex nor concave:
FunctionConvexity[FactorialPower[x, 3], x]TraditionalForm formatting:
FactorialPower[x, n]//TraditionalFormFactorialPower[x, n, h]//TraditionalFormDifferentiation (3)
First derivative of
with respect to
:
D[FactorialPower[x, n], x]First derivative of
with respect to
:
D[FactorialPower[x, n], n]Higher derivatives of
with respect to
:
Table[D[FactorialPower[x, n], {x, k}], {k, 1, 3}]//FullSimplifyPlot the higher derivatives with respect to x when n=2:
Plot[Evaluate[% /. n -> 1 / 2], {x, -3, 0}, PlotLegends -> {"First Derivative", "Second Derivative", "Third Derivative"}]Series Expansions (4)
Find the Taylor expansion using Series:
Series[FactorialPower[x, n], {x, 0, 2}]//Normal// FullSimplifyPlots of the first two approximations around
:
funcAndSeries = Prepend[Table[Series[FactorialPower[x, 3], {x, 0, m}], {m, 1, 2}], FactorialPower[x, 3]]//Normal;
Plot[funcAndSeries, {x, -10, 10}]Taylor expansion at a generic point:
Series[FactorialPower[x, n], {x, x0, 2}]//Normal// FullSimplifySeries expansion at a singular point:
Series[FactorialPower[x, 4], {x, -1, 3}]FactorialPower can be applied to a power series:
FactorialPower[x + O[x] ^ 5, 10]Applications (4)
The number of length-r permutations of a length-n list of distinct elements is given by FactorialPower[n,r]:
Length[Permutations[Range[5], {3}]]FactorialPower[5, 3]The number of triples of distinct digits:
FactorialPower[10, 3]Count[Tuples[Range[10], {3}], x_ /; DeleteDuplicates[x] === x]Approximate a function using Newton's forward difference formula [MathWorld]:
delta[k_, x_] = DifferenceDelta[Sin[x], {x, k}]Construct an approximation by truncating the series:
approx[a_] = Sum[(FactorialPower[a, k]/k!)delta[k, 0], {k, 0, 10}];Plot[{Sin[a], approx[a]}, {a, -Pi / 2, Pi / 2}]Table[NorlundB[n, n], {n, 10}]Compare with their integral definition:
Table[Integrate[FactorialPower[x - 1, n], {x, 0, 1}], {n, 10}]//FunctionExpandProperties & Relations (11)
FactorialPower is to Sum as Power is to Integrate:
Sum[FactorialPower[x, 5], x]Integrate[x ^ 5, x]FactorialPower satisfies
:
DifferenceDelta[FactorialPower[x, n], x]This makes FactorialPower analogous to Power and its relationship to D:
D[x ^ n, x]FactorialPower can always be expressed as a ratio of gamma functions:
FunctionExpand[FactorialPower[x, n]]Compare with the expansion of
:
FunctionExpand[Pochhammer[x - n + 1, n]]FactorialPower[x,n] is equivalent to
:
FullSimplify[FactorialPower[x, n] == n!Binomial[x, n]]FactorialPower[x,x] is equivalent to x!:
FunctionExpand[FactorialPower[x, x]]FunctionExpand[x!]Pochhammer can be expressed in terms of a single FactorialPower expression:
Pochhammer[a, n] == FactorialPower[a + n - 1, n]//FullSimplifyVerify the identity
for integer
:
FullSimplify[Pochhammer[x, k] == FactorialPower[x, k, -1]//FunctionExpand, k∈ℤ]This function is often called the rising factorial:
FactorialPower[x, 5, -1]//FunctionExpandVerify an expansion of FactorialPower in terms of Pochhammer for the first few cases:
Table[FactorialPower[x, n] == Underoverscript[∑, k = 0, n](-1)^n - k(n!/k!)Binomial[n - 1, k - 1]Pochhammer[x, k]//FunctionExpand//Simplify, {n, 0, 9}]FactorialPower can be represented as a DifferenceRoot:
DifferenceRootReduce[FactorialPower[k, z], k]DifferenceRootReduce[FactorialPower[z, k], k]The generating function for FactorialPower:
GeneratingFunction[FactorialPower[n, k], n, x]The exponential generating function for FactorialPower:
ExponentialGeneratingFunction[FactorialPower[n, k], n, x]Possible Issues (2)
Generically, Power is recovered as the limit as
of FactorialPower:
Series[FactorialPower[x, a, h], {h, 0, 1}]This may not be true, however, if
is kept on the negative real axis:
N[FactorialPower[-1 / 3, 1 + I, 10^-7], 20]N[(-1 / 3)^1 + I, 20]The generic series expansion around the origin may not be defined at integer points:
Series[FactorialPower[x, n], {x, 0, 2}]Quiet[% /. n -> 2]Use assumptions to refine the result:
Assuming[Element[n, Integers] && n > 0, Series[FactorialPower[x, n], {x, 0, 2}]]% /. n -> 2Compare with the expansion for an explicit value of
:
Series[FactorialPower[x, 2], {x, 0, 2}]Related Links
History
Text
Wolfram Research (2008), FactorialPower, Wolfram Language function, https://reference.wolfram.com/language/ref/FactorialPower.html.
CMS
Wolfram Language. 2008. "FactorialPower." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/FactorialPower.html.
APA
Wolfram Language. (2008). FactorialPower. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/FactorialPower.html
BibTeX
@misc{reference.wolfram_2026_factorialpower, author="Wolfram Research", title="{FactorialPower}", year="2008", howpublished="\url{https://reference.wolfram.com/language/ref/FactorialPower.html}", note=[Accessed: 12-June-2026]}
BibLaTeX
@online{reference.wolfram_2026_factorialpower, organization={Wolfram Research}, title={FactorialPower}, year={2008}, url={https://reference.wolfram.com/language/ref/FactorialPower.html}, note=[Accessed: 12-June-2026]}