When learning algorithms, such as RSA, it is important to understand the mathematics being used. In RSA, the number of positive integers less than or…

Euler's totient

https://en.wikipedia.org/wiki/Euler%27s_totient_function

In number theory, Euler's totient function counts the positive integers up to a given integer n that

are relatively prime to n.

Incorrect answers:

Fibonacci number - commonly denoted Fn, form a sequence, called the Fibonacci sequence, such

that each number is the sum of the two preceding ones, starting from 0 and 1.

Fermat's number - named after Pierre de Fermat, who first studied them, is a positive integer of the

form Fn = 2^2^n+1 where n is a non-negative integer. The first few Fermat numbers are:

3, 5, 17, 257, 65537, 4294967297, 18446744073709551617, …

Mersenne prime – prime number that is one less than a power of two. That is, it is a prime number

of the form Mn = 2^n − 1 for some integer n. They are named after Marin Mersenne, a French Minim

friar, who studied them in the early 17th century.