Figure skating jumps
Jumps are referred to by how many times the skater turns in the air. One revolution (one and a half for the Axel) is a "single" jump. Two revolutions (two and a half for the Axel) is a "double" jump. Three revolutions (three and a half for the Axel) is a "triple" jump. Four revolutions (four and a half for the Axel, although this has never been done in competition) is a "quadruple" or "quad" jump. The first triple jump landed in competition was a loop jump. It was landed by Dick Button in 1952. The first quadruple jump landed in competition was a toe loop jump. It was landed by Kurt Browning in 1988. Currently, men in world-class competition usually attempt a full set of triples and sometimes one or two quadruple jumps in their free skating programs. Triple Axels are rare for ladies, and quadruple jump attempts even more so.
Magic square
The order four magic square Albrecht Dürer immortalized in his 1514 engraving "Melencolia I,", referred to above, is believed to be the first seen in European art. The square associated with Jupiter appears as a talisman used to drive away melancholy. It is very similar to Yang Hui's square, which was created in China about 250 years before Dürer's time. The sum 34 can be found in the rows, columns, diagonals, each of the quadrants, the center four squares, and the corner squares (of the 4×4 as well as the four contained 3×3 grids). This sum can also be found in the four outer numbers clockwise from the corners (3+8+14+9) and likewise the four counter-clockwise (the locations of four queens in the two solutions of the 4 queens puzzle), the two sets of four symmetrical numbers (2+8+9+15 and 3+5+12+14), the sum of the middle two entries of the two outer columns and rows (5+9+8+12 and 3+2+15+14), and in four kite or cross shaped quartets (3+5+11+15, 2+10+8+14, 3+9+7+15, and 2+6+12+14). The two numbers in the middle of the bottom row give the date of the engraving: 1514. The numbers 1 and 4 at either side of the date correspond respectively to the letters "A" and "D," which are the initials of the artist.