# Defining Riemann sums using summation notation causes incorrect index for the first two terms of the sum

**URL:** <https://cl.desmos.com/t/defining-riemann-sums-using-summation-notation-causes-incorrect-index-for-the-first-two-terms-of-the-sum/7345>\
**Category:** Bug Reports\
**Created:** [October 1, 2024, 11:13pm UTC](https://cl.desmos.com/t/defining-riemann-sums-using-summation-notation-causes-incorrect-index-for-the-first-two-terms-of-the-sum/7345 "2024-10-01T23:13:30Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Zac\_Bettersworth](https://yyz1.discourse-cdn.com/flex031/user_avatar/cl.desmos.com/zac_bettersworth/32/6092_2.png) [@Zac\_Bettersworth](https://cl.desmos.com/u/Zac_Bettersworth)\
**Post date:** [October 1, 2024, 11:13pm UTC](https://cl.desmos.com/t/defining-riemann-sums-using-summation-notation-causes-incorrect-index-for-the-first-two-terms-of-the-sum/7345/1 "2024-10-01T23:13:30Z")

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Something’s not working the way it seems like it should.

When I was using Desmos to create an activity for integration, accumulation functions, and partial sums…

I saw that the first two terms of the sum were incorrect (the summation appeared to be pulling the first two terms using k = 1 and k = 1 instead of k = 1 and k = 2), but would fix itself for later indices.

Here’s the link to the initial activity where I noticed the index issue:  
https://www.desmos.com/calculator/qk8dtttx9u?embed  
Here’s the link to the second activity which I used to troubleshoot the error:  
https://www.desmos.com/calculator/czzw0ywijc?embed

Thanks!