Fatto generale: 261 is number of possible unfolded tesseract patterns.
Fatto matematico: 261 is the number of essentially different ways to dissect a 16-gon into 7 quadrilaterals.
Trivia: 261 is number of possible unfolded tesseract patterns.
Data storica: September 17th is the day in 2001 that the New York Stock Exchange reopens for trading after the September 11 Attacks, the longest closure since the Great Depression.