Number Theory
Basic

Triangular Number

Sum of the first n natural numbers.

Formula

Tn=n(n+1)2T_n = \frac{n(n+1)}{2}

Variables

nIndex

Example

T_4 = 10

Did You Know?

The young Gauss reportedly summed 1 to 100 in seconds by pairing terms, discovering triangular numbers.

figuratesequence