One pair.
2 5 6
Eight pairs.
5, 7 11, 13 17, 19
When their GCF is greater than 1. When they have prime factors in common.
(2,3) and (2,5) are the two pairs such that the sum of their elements is a prime number.
They are: 3, 5 and 7
There are eight twin prime pairs less than 100 [(3, 5), (5, 7), (11, 13), (17, 19), (29, 31), (41, 43), (59, 61), and (71, 73)].
There are 25 prime numbers less than 100
There are 35 prime numbers less than 150.
The prime numbers less then 86 are; 2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79 and 83.
There are 46 prime numbers less than 200.
1 3 5 7 11 13 17 19