Easy does it! The Smart Scholar Method

Take 1, 2. The result, if the operation is performed, can be seen to be 2.

Take 1, 2, 3. The result is 4.

Take 1, 2, 3, 4. The result is 7.

Take 1, 2, 3, 4, 5. The result is 11.

Take 1, 2, 3, 4, 5, 6. The result is 16.

Take 1, 2, 3, 4, 5, 6, …, n. The result is n*(n+1)/2 – (n – 1) = (n^2 – n + 2)/2.

For n = 40, the result is 781.

For our result, we need to add 315 to each of these. Thus 315*40 + 781 = 13381.

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