Question 20
a) Several distinct positive integers have the property that the sum of every three of them is a prime number. At most how many of them are there?
b) Several distinct integers (not necessarily positive) have the property that the sum of every three of them is positive and also a prime number. At most how many of them are there?
b) Several distinct integers (not necessarily positive) have the property that the sum of every three of them is positive and also a prime number. At most how many of them are there?