As the sum of the first five pentagonal numbers, seventy-five is a pentagonal pyramidal number. It can also be categorized as a self, Keith, and enneagonal number. If any of these terms have meaning to you whatsoever, you’ll probably enjoy the science, medicine, and natural history served up in the seventy-fifth edition of the Tangled Bank, hosted by Grrlscientist at Living the Scientific Life.

Written by Mike
Mike is a leading authority in the field of standardized test preparation, but he's also a traveler who fully expects to see every bird in the world. Besides founding 10,000 Birds in 2003, Mike has also created a number of other entertaining but now extirpated nature blog resources, particularly the Nature Blog Network and I and the Bird.