What is the value of `a_7` if `a_n`=`1+(-1)^n`?

What is the value of,Lt_(n rarr oo)sum_(r=1)^(n)(1)/(n)e^((r)/(n))

FOr an integer nlt2, we have real numbers a_1,a_2,a_3,a_4,..........,a_n such that a_2+a_3+a_4+.......+a_n=a1 and a_1+a_3+a_4+...........+a_n=a_2...............a_1+a_2+a_3+..............+a_(n-1)=a_n what is the value of a_1+a_2+a_3+........+a_n?

If N = ( sqrt7 - sqrt3) //(sqrt7 + sqrt3), then what is the value of N + (1/N)?

What is the value of (1)/(log_(2)n)+(1)/(log_(3)n)+ . . .+(1)/(log_(40)n) ?

If N = sqrt7 - sqrt3 , then what is the value of (1/N)?

If a_1, a_2, a_3..... a_n in R^+ and a_1.a_2.a_3.........a_n = 1, then minimum value of (1+a_1 + a_1^2) (1 + a_2 + a_2^2)(1 + a_3 + a_3^2)........(1+ a_n + a_n^2) is equal to :-

If a_1+a_2+a_3+......+a_n=1 AA a_1 > 0, i=1,2,3,......,n, then find the maximum value of a_1 a_2 a_3 a_4 a_5......a_n.