# HarmonicNumber

gives the n harmonic number .

HarmonicNumber[n,r]

gives the harmonic number of order r.

# Details • Mathematical function, suitable for both symbolic and numerical manipulation.
• The harmonic numbers are given by with .
• HarmonicNumber can be evaluated to arbitrary numerical precision.
• HarmonicNumber automatically threads over lists.
• HarmonicNumber can be used with Interval and CenteredInterval objects. »

# Examples

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## Basic Examples(7)

First ten harmonic numbers:

Plot over a subset of the integers:

Plot over a subset of the complexes:

Series expansion at the origin:

Series expansion at Infinity:

Series expansion at a singular point:

Carry out sums involving harmonic numbers:

## Scope(34)

### Numerical Evaluation(5)

Evaluate numerically:

Evaluate to high precision:

The precision of the output tracks the precision of the input:

Complex number input:

Evaluate efficiently at high precision:

HarmonicNumber can be used with Interval and CenteredInterval objects:

### Specific Values(5)

HarmonicNumber[n,a] for symbolic a:

HarmonicNumber[n,a] for symbolic n:

Value at zero:

Find a value of n for which HarmonicNumber[n]=1.5:

Express harmonic numbers of fractional argument in terms of elementary functions:

### Visualization(3)

Plot the HarmonicNumber function:

Plot the HarmonicNumber function for various orders:

Plot the real part of HarmonicNumber:

Plot the imaginary part of HarmonicNumber:

### Function Properties(11)

Real domain of HarmonicNumber:

Complex domain:

Real range of HarmonicNumber:

HarmonicNumber threads elementwise over lists and arrays:

HarmonicNumber is not an analytic function:

However, it is meromorphic:

HarmonicNumber is neither non-increasing nor non-decreasing:

HarmonicNumber is not injective:

HarmonicNumber is surjective:

HarmonicNumber is neither non-negative nor non-positive:

HarmonicNumber has both singularities and discontinuities for negative integers:

HarmonicNumber is neither convex nor concave:

### Differentiation(3)

First derivative with respect to n:

Higher derivatives with respect to n:

Plot the higher derivatives with respect to n:

Formula for the  derivative with respect to n:

### Integration(3)

Compute the indefinite integral using Integrate:

Verify the anti-derivative:

Definite integral:

More integrals:

### Series Expansions(2)

Find the Taylor expansion using Series:

Plots of the first three approximations around :

General term in the series expansion using SeriesCoefficient:

### Function Identities and Simplifications(2)

The defining identity for HarmonicNumber:

Recurrence identities:

## Generalizations & Extensions(5)

### Harmonic Numbers(2)

Series expansion at infinity:

HarmonicNumber can be applied to power series:

### Harmonic Numbers of Order r(3)

Evaluate at exact arguments:

Series expansion at any point:

Series expansion at infinity:

## Applications(5)

The average number of comparisons in Quicksort:

Plot over the complex plane:

Book stacking with the maximal overhang:

Pick the best candidate out of n candidates after x evaluated choices [more info]:

Evaluate for n=100:

Plot as a function of harem size:

A finite sum with StirlingS1 expressed in terms of HarmonicNumber:

A finite sum with StirlingS2 expressed in terms of HarmonicNumber:

## Properties & Relations(10)

HarmonicNumber can be expressed in terms of PolyGamma:

HarmonicNumber can be expressed in terms of Zeta and HurwitzZeta:

Use FullSimplify to simplify expressions containing harmonic numbers:

Expand in simpler functions:

Sums:

Generate from sums and integrals:

HarmonicNumber can be represented as a DifferenceRoot:

General term in the series expansion of HarmonicNumber:

The ordinary generating function for HarmonicNumber:

The exponential generating function for HarmonicNumber:

## Possible Issues(3)

Large arguments can give results too large to be computed explicitly: Machine-number inputs can give highprecision results:

Results are often expressed in terms of PolyGamma instead of HarmonicNumber: