1985 AIME Problem 13

The numbers in the sequence 101,104,109,116, \ldots are of the form a_{n}=100+n^{2}, where n=1,2,3, \ldots. For each n, let d_{n} be the greatest common divisor of a_{n} and a_{n+1}. Find the maximum value of d_{n} as n ranges through the positive integers.