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The triangular numbers are

1, 3, 6, 10, 15, ...

and are calculated as:

t1 = 1

t2 = 1 + 2

t3 = 1 + 2 + 3

tn = 1 + 2 + ... + n

The formula for the sum tn = 1 + 2 + ... + n is:

tn = n(n+1)/2

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14y ago

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