Question 798918
This is 1 + 2 + 3 + 4 + 5 + 6  . . . 
The formula ( which I happen to know ) is
Sum = {{{ ( n*( n + 1 )) / 2 }}}
If {{{ n = 6 }}}, the sum is {{{ 21 }}}
Sum = {{{ ( 6*7 ) / 2 = 21 }}}