27

Part of 2003 Iran MO (3rd Round)

Problems(1)

Source: Iranian National Olympiad (3rd Round) 2003

S\subset\mathbb N

is called a square set, iff for each

x,y\in S

, xy\plus{}1 is square of an integer. a) Is

S

finite? b) Find maximum number of elements of

S

number theory proposednumber theory