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 1462 that the Battle of Świecino (also known as the Battle of Żarnowiec) is fought during Thirteen Years' War.