Octagonal number
= Octagonal number
{wiki=Octagonal_number}
An octagonal number is a type of figurate number that represents a regular octagon. The \\( n \\)-th octagonal number can be calculated using the formula: \\\[ O_n = n(3n - 2) \\\] where \\( O_n \\) is the \\( n \\)-th octagonal number and \\( n \\) is a positive integer (1, 2, 3, ...).