4thtriangularnumber

<-- Enter triangular number statement
  

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Calculate triangular number 4

The formula for triangular number n is as follows

Tn  =	n(n + 1)
	2

Given n = 4, we have:

T4  =	4(4 + 1)
	2

T4  =	4(5)
	2

T4  =	20
	2

T₄ = 10

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