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2019-06-25 15:55:24 +0200 | asked a question | 3-d bezier-path made thick I want to draw a $3$-dimensional bezier path with
recommended in the manual. It seems however, that the thickness does not change. What do you suggest? |

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2018-06-06 16:12:15 +0200 | asked a question | More problems with general power of a matrix Even though in version 8.2 the code for the general power of a matrix has been improved (c.f. question 41622), it still doesn't work in some cases, as i.e. this singular, diagonalizable matrix shows. Concerning the remark in trac ticket 25520: Why not defining $0^x=1$ for $x\in {\bf N}$, which seems reasonable, since the number of functions $\emptyset \to \emptyset$ is 1? |

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2018-03-31 21:49:26 +0200 | asked a question | Combinatorial Species of Phylogenetic Trees I would like to study the combinatorial class ${\cal H}$ of labelled phylogenetic trees, defined as rooted trees, whose internal nodes are unlabelled and are constrained to have outdegree $\geq 2$, while their leaves have labels attached to them. According to Flajolet, Sedgewick:
The number of labelled structures is given by the integer sequence. In particular I tried to calculate (for a small cardinal number) - a list of such structures.
- a generating series of this structures.
- the number of such structures.
- isomorphism-types of such structures.
- a generating series of the isomorphism-types of such structures.
- a random such structure.
- automorphism-groups of of such structures.
using the following code: Only 2. seems to work. If my code ist correct, I wonder if some of these (i.e. composition species) are not implemented and when (whether) they will be. |

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2018-03-22 22:43:07 +0200 | edited question | Bug in general power of a matrix The code to question 35658 gives a wrong answer i.e. for the matrix Where can I find an improvement? For $k\in {\bf N}$ the $k$-th power of a matrix $A\in {\bf R}^{n\times n}$ satisfies by definition the recursion $A^{k+1}=A*A^k$ and the initial condition $A^0=I$. Substitution of $k=0$ and $k=1$ should therefore give the identity matrix $I$ resp. the matrix $A$. The following live code does (currently) not give the expected answer. Btw: One of the M-programs gives the correct answer. |

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