# Guest Post: Spooky Math

Today’s guest post comes from Madison Hodson, an instructor at AcerPlacer who studies mathematics at Weber State University.

What do you get when you divide the circumference of a pumpkin by it’s diameter..? Pumpkin Pie! It’s Maddy here, and since it’s Halloween, I thought I would open up this little article with a Halloween math joke – I’ll try to keep the theme of connecting Halloween and math going throughout the article. Thanks to the internet, I was able to do a little research and find out some weird, creepy, and spooky facts about some numbers!

### Vampire Numbers

A number v = xy with an even number of n digits formed by multiplying a pair of  n/2 digit numbers (where the digits are taken from the original number in any order) x and y together. If v is a vampire number then x and y are called its “fangs.”

• 21 × 60 = 1260
• 41 × 35 = 1435
• 15 × 93 = 1395
• 30 × 51 = 1530

### Tombstone

Also known as the halmos symbol, the tombstone ▮ indicates the end of a proof.

### Napier’s Bones

An abacus created by John Napier used to calculate the product and quotients of numbers.

### Devil’s Staircase

The Devil’s Staircase, also known as the Cantor Function, is an example of a function that is continuous, but not absolutely continuous.

### Witch of Agnesi

A curve studied by Maria Agnesi in 1748 in her book Instituzioni analitiche ad uo della gioventù italiana (the first surviving mathematical work written by a woman). The Cartesian equation is  $\inline y=\dfrac{8a^3}{x^2+4a^2}$