N=(5^2)*(3^2n+1)*(2^n)-(3^n)*(6^n+2)
=25*3^(2n+1)*2^n-3^n*2^(n+2)*3^(n+2)
=3^(2n+1)*2^n(25-3*2^2)
=3^(2n+1)*13
所以能被13整除