The explicit formula for calculating the sum is
The sum of the nth term of a sequence is expressed as;
a is the first term
d is the common difference
n is the number of terms
For the sequence 0 + 1 + 2 + 3 +...
Similarly for the sequence:
1 + 2+ 3 + 4+...
Taking the product of the sum to get the explicit formula for calculating the sum
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