a1=1/(3+√3)a2=1/(5√3+3√5)an=1/[(2n+1)√(2n-1)+(2n-1)√(2n+1)] =[(2n+1)√(2n-1)-(2n-1)√(2n+1)]/[(2n+1)^2(2n-1)-(2n-1)^2(2n+1)] =(1/2)[1/√(2n-1)-1/√(2n+1)]a1+a2+..+a49=(1/2)(1-1/√99)
