St Paul's Cathedral familiar with the unique octagonal lantern tower over the crossing of Ely Cathedral, which spans the aisles as well as the central nave, unlike the central towers and domes of most churches. Wren adapted this characteristic in designing the dome of St Paul's. In section St Paul's also maintains a medieval form, having the aisles much lower than the nave, and a defined clerestory. The most notable exterior feature is the dome, which rises to the cross at its summit, and dominates views of the City. The height of 365 feet is explained by Wren's interest in astronomy. Until the
Octagonal number pronic number. Octagonal numbers consistently alternate parity. Octagonal numbers are occasionally referred to as "star numbers," though that term is more commonly used to refer to centered dodecagonal numbers. Solving the formula for the "n"-th octagonal number, formula_2 for "n" gives An arbitrary number "x" can be checked for octagonality by putting it in this equation. If "n" is an integer, then "x" is the "n"-th octagonal number. If "n" is not an integer, then "x" is not octagonal. Octagonal number An octagonal number is a figurate number that represents an octagon. The octagonal number for "n" is given by