The distance from the center of the circle to the straight line is |n+ 1|/ root number 2.
(|n+ 1|/ root 2) 2+ (root number 2) 2 = n 2+1.
n^2+2n+ 1+4=2n^2+2
n^2-2n-3=0
N=- 1 or 3 (exclusive)
(x+ 1)^2+y^2=2