Use summation notation to write the following series?

4 + 7 + 10 + 13 + 16 + 19

I know how to expand series in summation notation and simplify but I don't know how to do it in reverse.

1 Answer
Apr 12, 2018

sum_(n=1)^6 3n+1

Explanation:

The terms are increasing by 3 so look for a pattern that involves times3.

4=3times1+1
7=3times2+1
10=3times3+1
...
19=3times6+1

So, 4+7+10+13+16+19=sum_(n=1)^6 3n+1