Dodecagonal number explained

A dodecagonal number is a figurate number that represents a dodecagon. The dodecagonal number for n is given by the formula

D _{n} =5 n ^{2} - 4 n

The first few dodecagonal numbers are:

0, 1, 12, 33, 64, 105, 156, 217, 288, 369, 460, 561, 672, 793, 924, 1065, 1216, 1377, 1548, 1729, ...

Properties

• The dodecagonal number for n can be calculated by adding the square of n to four times the (n - 1)th pronic number, or to put it algebraically,

D _{n} = n ^{2} + 4 (n ^{2} - n) .

• Dodecagonal numbers consistently alternate parity, and in base 10, their units place digits follow the pattern 1, 2, 3, 4, 5, 6, 7, 8, 9, 0.
• By the Fermat polygonal number theorem, every number is the sum of at most 12 dodecagonal numbers.

D _{n} is the sum of the first n natural numbers congruent to 1 mod 10.D _{n+1} is the sum of all odd numbers from 4n+1 to 6n+1.

See also

• Polygonal number
• Figurate number
• Dodecagon