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Sum of Triangular Numbersο
Your task is to return the sum of Triangular Numbers
up-to-and-including the nth Triangular Number.
Triangular Number: βany of the series of numbers (1, 3, 6, 10, 15, etc.)
obtained by continued summation of the natural numbers 1, 2, 3, 4, 5, etc.β
[01]02
[03]04 05
[06]07 08 09
[10]11 12 13 14
[15]16 17 18 19 20
[21]
e.g. If 4 is given: 1 + 3 + 6 + 10 = 20.
Triangular Numbers cannot be negative so return 0 if a negative number is given.