1.Previous
3.Next

is a trapezoidal number.

The pattern found for triangular numbers and for tetrahedral numbers which uses binomial coefficients, can be generalized. This leads to the formula:

Other properties

Triangular numbers correspond to the first-degree case of Faulhaber's formula. Alternating triangular numbers (1, 6, 15, 28, ...) are also hexagonal numbers.

Every even perfect number

1.Previous
3.Next