The snow, collecting in triangles on the fence like this, reminds me a bit of Sierpinski’s triangle.
Appreciation Numbers
01/24/2014 — Happy Permutation Day!
Today we celebrate a Permutation Day! I call days like today permutation days because the digits of the day and month can be rearranged to form the year.
Celebrate Permutation Day by mixing things up! Try doing things in a different order today. Just remember, for some operations, order definitely matters!
Appreciation Art
Math Art: Triangular String Sculpture
This sculpture is by David H Press. You can find out more about his work here.
This is another piece from the 2013 Bridges Mathematical Art Gallery.
Appreciation Numbers
12/30/2013 — Happy Derangement Day!
Today we celebrate a Derangement Day! Usually I call days like today a permutation day because the digits of the day and month can be rearranged to form the year, but there’s something extra special about today’s date:
The numbers of the month and day are a derangement of the year: that is, they are a permutation of the digits of the year in which no digit remains in its original place!
Derangements pop up in some interesting places, and are connected to many rich mathematical ideas. The question “How many derangements of n objects are there?” is a fun and classic application of the principle of inclusion-exclusion. Derangements also figure in to some calculations of e and rook polynomials.
So enjoy Derangement Day! Today, it’s ok to be totally out of order.
