Triangular Number Calculator
Find the nth triangular number, the sum of integers from 1 through n.
Formula
Tₙ = n(n+1)/2
Triangular number Tₙ ≈ (10)×((10)+1)÷2
How to use
- Enter a nonnegative integer n.
- Use n = 0 for the empty sum.
- Read the nth triangular number.
Examples
- n = 100 gives 5,050.
Frequently asked questions
Why is it called triangular?
Rows of 1, 2, …, n dots form a triangle.
What is the tenth triangular number?
It is 55, the sum 1+2+…+10.
Can n be a fraction?
No. The index counts whole rows; this form allows 0 to 10,000,000.
Sources
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