Tell me your solution to this problem:

Let the natural sequence be: A 1, A2, …A(2n+ 1),

Then the median term of 2n+ 1 number =a /(2n+ 1)

b = {[a(n+2)]^2-[a 1]^2}+…+{[a(2n+ 1)]^2+[ an]^2}

=(n+ 1)*[A 1+A(n+2)]+…+(n+ 1)*[An+A(2n+ 1)]

=(n+ 1)[A 1+A2+…+An+A(n+2)+…+A(2n+ 1)]

=(n+ 1)[a - a/(2n+ 1)]

=2na(n+ 1)/(2n+ 1)

Therefore, because b/a=60/ 1 1, 2n (n+1)/(2n+1) = 60/1.

Simplification: 1 1n 2-49n-30 = 0

(n-5)*( 1 1n+6)=0

Solution: n = 5；; (negative root removal)

Answer: n=5