Explore the visual representation of finding the sums:[br][br]1[br]1+2[br]1+2+3[br]1+2+3+4[br]...[br]1+2+3+4+5+6+7+8+9+10[br][br]Or, in other words, finding the first 10 partial sums of the arithmetic sequence [math]a_n = n[/math]

Write a formula for each partial sum, and generalize this to the [math]n^{th}[/math] partial sum.