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Illustrating the Padovan sequence

The Padovan sequence is a cousin of the more famous Fibonacci sequence defined by the initial values $P(1)=P(2)=P(3)=1$ and the recurrence relation $P(n) = P(n-2) + P(n-3)$. That is, the next value is obtained not by summing the previous two values but by summing the two values before the last one. The first few values are:

Plotting COVID-19 case growth charts

Following on from this previous post, here is a short tutorial on creating this and similar charts using pandas by automatically downloading data from Johns Hopkins University's CSSE GitHub repository (the "JHU/CSSE dataset").

Plotting COVID-19 cases

The Centre for Systems Science and Engineering (CSSE) at Johns Hopkins University publishes daily statistics of the number of confirmed cases of COVID-19 by country on its GitHub page. The short script below pulls data from this page to plot a bar chart of cases and growth in cases as a function of time for a given country. For example:

The Trapped Knight

The Trapped Knight problem is a chess-based problem apparently invented by Neil Sloane and giving rise to a finite number sequence in his Online Encyclopedia of Integer Sequences (OEIS A316667).

PyValem: a Python package for parsing chemical formulas and states

PyValem is a Python package, for parsing, representing and manipulating the formulas of simple chemical species, their states and reactions. Its source is available on GitHub under a GPL licence, and it can be installed from the Python Package Index, PyPI, using pip: