# Questions tagged [series-expansion]

Questions on dealing with series data and constructing power series expansions of functions.

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### Series expansion of Lerch transcendent still buggy?

This series expansion of a Lerch transcendent seems fixed in V12. However, the following still fails: From the definition of a Lerch transcendent, ...
71 views

### Implement Baker-Campbell-Hausdorff expansion

I wish to calculate the recursive formula, $$\mathrm{e}^{-A_1 \Delta t/2}\mathrm{e}^{-A_0 \Delta t/2}B\mathrm{e}^{A_0 \Delta t/2}\mathrm{e}^{A_1 \Delta t/2}$$ with the BCH expansion to second order ...
31 views

### Fast way to the Taylor series expansion coefficients of multi-variable function? [duplicate]

Is there a fast method to get the coefficients of Taylor series expansion of function $f(x_1,x_2,...,x_d)$ with maximal summed partial derivative up to $n$, where $d,n$ can be relatively large (for ...
39 views

### Number-theoretic notation in Wolfram Cloud for iOS

I am using Wolfram Cloud Mathematica, and I want to write an equation using the mathematical symbols for Sum (like a capital sigma, but no the Greek letter) and <...
57 views

### Strange behaviour of infinite sum (H[n]- Series[H[n]])

Bug report filed 14.01.2020 A support case was created with the ID [CASE:4371991] EDIT It is easy to show that the workaround "limit of finite sum" proposed in the solution by user64494 leads to ...
33 views

### Series of implicit function (Puiseux expansion) - problem

This two one-line codes should represent the same thing, i.e. the first root of polynomial in $y$: ...
43 views

196 views

### Eigenvectors in the limit $\mu\rightarrow 0$ are not the same as eigenvectors when setting $\mu=0$ from the beginning

I would like to find the eigenvectors of a matrix and see what the eigenvectors look like in the limit of $\mu\rightarrow 0$: ...