English Gothic architecture Exeter Cathedral is built in this style, as is the crossing of Ely Cathedral, (including the famous octagonal lantern, built between 1322 and 1328 to replace the fallen central tower), three west bays of the choir and the Lady Chapel. In Scotland, Melrose Abbey was a noteworthy example, though much of it is now in ruins. The Perpendicular Gothic period (or simply Perpendicular) is the third historical division of English Gothic architecture, and is so-called because it is characterised by an emphasis on vertical lines. An alternative name, the Rectilinear, was suggested by Edmund Sharpe, and is preferred by some
Octagonal number Octagonal number An octagonal number is a figurate number that represents an octagon. The octagonal number for "n" is given by the formula 3"n" - 2"n", with "n" > 0. The first few octagonal numbers are: 1, 8, 21, 40, 65, 96, 133, 176, 225, 280, 341, 408, 481, 560, 645, 736, 833, 936 Octagonal numbers can be formed by placing triangular numbers on the four sides of a square. To put it algebraically, the "n"-th octagonal number is The octagonal number for "n" can also be calculated by adding the square of "n" to twice the ("n - 1")th