Dominoes spots from one to six are generally arranged as they are on six-sided dice, but because blank ends having no spots are used, seven faces are possible, allowing 28 unique pieces in a double-six set. However, this is a relatively small number especially when playing with more than four people, so many domino sets are "extended" by introducing ends with greater numbers of spots, which increases the number of unique combinations of ends and thus of pieces. Each progressively larger set increases the maximum number of pips on an end by three, so the common extended sets are double-nine, double-12,
How Many Billboards? Art Instead How Many Billboards? Art Instead How Many Billboards? Art Instead, was a large scale urban art exhibition in Los Angeles, California. The exhibition, which opened in February 2010, concurrently displayed 21 unique billboards created by various leading contemporary Californian artists. Organized by MAK Center director Kimberli Meyer and co-curated by Nizan Shaked and Dr. Gloria Sutton, the exhibition asked artists "to create a new work that critically responded to the medium of the billboard and interpreted its role in the urban landscape". Notable contemporary artist Martha Rosler and her son Josh Neufeld were among some of the commissioned artists. https://www.fastcompany.com/1559860/los-angeles-swaps-21-billboards-art