484 HISTORY OF THE THEORY OF NUMBERS. [CHAP, xvi 



A. C. L. Wilkinson 141 made 2y 2 -z 2 and 2z 2 y 2 +l squares x 2 and u 2 . 

 Putx = a+b,z = a-b. Then x 2 +z 2 = 2y 2 gives a 2 +b 2 = y 2 ; a, y = k(m 2 =Fn 2 ); 

 b = 2kmn. Take ra = 9, n = 7. Then w 2 = 193(2/b) 2 +l. By the continued 

 fraction for Vl93, u = 6224323426849, A; = 224018302020. 



A. GSrardin and R. Goormaghtigh 142 treated 



(y-x) 2 +x = A*, (y-x) z -y=B 2 . 

 Add and set t = x y; then 2P+t = A 2 +5 2 , an easy problem. 



141 Jour. Indian Math. Club, 2, 1910, 193. 



142 L'intermdiaire des math., 22, 1915, 193; 24, 1917, 84-5. 



