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Consider this pattern where the positive, odd integers are arranged in a triangular formation. The 1st through 4th rows are shown; each row has one more entry than the previous row. What is the sum of the integers in the 15th row?

 

1

3 5

7 9 11 

13 15 17 19

...

 May 28, 2020
 #1
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Use this "closed form" formula to generate any line you want, then just list them and add them up:

 

a(n) =n^2 - n + 1. So, the 15th row looks like this:

 

15th row = (211, 213, 215, 217, 219, 221, 223, 225, 227, 229, 231, 233, 235, 237, 239)=3,375

 May 28, 2020

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