Best Of MetaFilter

seanmpuckett tells the story of how he wrote a BASIC program to play a Merlin-like game which made it into Computer magazine and was later the subject of an article in Mathematics Magazine.

Heat Pump Field Installation by Cushing Memorial Library and Archives, Texas A&M (cc by)

MeFite larkery explains some of the data you have to assess when considering whether a heat pump is worth the expense.

In conclusion: it's really hard to work out whether heat pumps are a good idea or not - you need a lot of different data to get a good result, and some of those data are hard to come by.

Sondra Eklund's prime factorization sweater.

This is a nice little find from Metafilter user Foci for Analysis this morning: a sweater which expresss the prime factors of the first hundred integers graphically. In base ten, and base eight on the back, and bases two and three on the sleeves while you're at it because why the heck not. The creator, Sondra Eklund, explains the visual methodology on her blog, and discusses the visual order in the colors and shapes:

The patterns are wonderful and fascinating. You’ll quickly notice that the yellows and the blues line up, because 5 and 2 are factors of 10. You also might notice that all perfect squares are symmetrical. Multiples of 11 go in a lovely pink diagonal across the sweater. There are hundreds more patterns.