A compilation of LEGO Technic parts to support learning experiments on linkages
Article by Zoltán Kovács and Benedek Kovács
In collections: Basically physics, Easily explained, Things to make and do, Geometry
We present a compilation of LEGO Technic parts to provide easy-to-build...
URL: arxiv.org/abs/1712.00440v1
PDF: arxiv.org/pdf/1712.00440v1

What are some of the most ridiculous proofs in mathematics?
Web page by Anonymous
In collections: The act of doing maths, About proof
URL: quora.com/Mathematics/What-are

Three Thoughts on “Prime Simplicity”
Article by Michael Hardy
In 2009, Catherine Woodgold and I published ‘‘Prime Simplicity’’, examining the belief that Euclid’s famous proof of the infinitude of prime numbers was by contradiction. We demonstrated that that belief is widespread among mathematicians...

A universal differential equation
Article by Lee A. Rubel
In collections: Fun maths facts, Unusual computers
There exists a non trivial fourth-order algebraic differential equation $P(y',y'',y''',y'''') = 0,$ where $P$ is a polynomial in four variables, with integer coefficients, such that for any continuous function $\phi$ on $(-\infty,\infty)$...
URL: projecteuclid.org/euclid.bams/

Useful inequalities cheat sheet
In collections: Lists and catalogues, About proof
This is a collection of some of the most important mathematical inequalities. I tried to include non-trivial inequalities that can be useful in solving problems or proving theorems. I omitted many details, in some cases even necessary conditions (hopefully only when they were obvious). If you are not...
URL: lkozma.net/inequalities_cheat_

New entry!
Fiboquadratic Sequences and Extensions of the Cassini Identity Raised From the Study of Rithmomachia
Article by Tomás Guardia and Douglas Jiménez
In collections: Fibonaccinalia, Games to play with friends, History
In this paper, we introduce fiboquadratic...
URL: arxiv.org/abs/1509.03177v3
PDF: arxiv.org/pdf/1509.03177v3

A cohomological viewpoint on elementary school arithmetic
Article by Isaksen, DC
In collection: Unusual arithmetic
URL: jstor.org/stable/10.2307/30723

Mechanical Computing Systems Using Only Links and Rotary Joints
Article by Ralph C. Merkle and Robert A. Freitas Jr. and Tad Hogg and Thomas E. Moore and Matthew S. Moses and James Ryley
In collections: Basically computer science, Things to make and do, Unusual computers
URL: arxiv.org/abs/1801.03534v1
PDF: arxiv.org/pdf/1801.03534v1

A Fresh Look at Peg Solitaire
Article by George I. Bell
In collections: Easily explained, Puzzles
URL: recmath.org/pegsolitaire/paper

Benjamin Peirce and the Howland will
Article by Meier, Paul and Zabell, Sandy
In collection: History
URL: jstor.org/stable/10.2307/22876
PDF: ben-israel.rutgers.edu/711/Mei

Undecidable problems: a sampler
Article by Poonen, Bjorn
In collection: Probability and statistics
After discussing two senses in which the notion of undecidability is used, we present a survey of undecidable decision problems arising in various branches of mathematics.
URL: arxiv.org/abs/1204.0299
PDF: arxiv.org/pdf/1204.0299v2

Irrationality From The Book
Article by Miller, Steven J. and Montague, David
In collections: About proof, Fun maths facts
We generalize Tennenbaum's geometric proof of the irrationality of sqrt(2) to sqrt(n) for n = 3, 5, 6 and 10.
URL: arxiv.org/abs/0909.4913
PDF: arxiv.org/pdf/0909.4913v2

Playing pool with $\pi$ (the number $\pi$ from a billiard point of view)
Article by Galperin, G
In collections: Easily explained, Fun maths facts
URL: turpion.org/php/reference.phtm

A categorical foundation for Bayesian probability
Article by Culbertson, Jared and Sturtz, Kirk
In collection: Probability and statistics
Given two measurable spaces $H$ and $D$ with countably generated $\sigma$-algebras, a prior probability measure $P_H$ on $H$ and a sampling distribution $\mcS:H \rightarrow D$, there is a corresponding...
URL: arxiv.org/abs/1205.1488
PDF: arxiv.org/pdf/1205.1488v3

Near Miss Polyhedra
Web page by Jim McNeill
In collections: The act of doing maths, Geometry
The polyhedra on this page are not quite regular, but as they are close I present them here as 'near misses'.
URL: orchidpalms.com/polyhedra/acro

Article by Fisher, GL and Mellor, B.
In collections: Easily explained, Things to make and do
URL: tandfonline.com/doi/abs/10.108

Random Triangles and Polygons in the Plane
Article by Jason Cantarella and Tom Needham and Clayton Shonkwiler and Gavin Stewart
In collections: Probability and statistics, Geometry
We consider the problem of finding the probability that a random triangle is obtuse, which was first raised by Lewis Caroll. Our investigation...
URL: arxiv.org/abs/1702.01027v1
PDF: arxiv.org/pdf/1702.01027v1

The general counterfeit coin problem
Article by Lorenz Halbeisen and Norbert Hungerbühler
In collections: Puzzles, Easily explained
Given $c$ nickels among which there may be a counterfeit coin, which can only be told apart by its weight being different from the others, and moreover $b$ balances. What is the minimal number of weighings...
URL: user.math.uzh.ch/halbeisen/pub

A game for budding knot theorists
Web page by Dave Richeson
In collection: Games to play with friends
URL: divisbyzero.com/2010/08/24/a-g

No, This is not a Circle
Article by Zoltán Kovács
In collections: Attention-grabbing titles, Easily explained, Drama!, Geometry
A curve, also shown in introductory maths textbooks, seems like a circle. But it is actually a different curve. This paper discusses some easy approaches to classify the result, including a GeoGebra applet...
URL: arxiv.org/abs/1704.08483v2
PDF: arxiv.org/pdf/1704.08483v2
A Mastodon instance for maths people. The kind of people who make $\pi z^2 \times a$ jokes.
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