"The function is usually denoted as \u03C6(n), a notation Gauss found after Euler formulated the function. It was first introduced as Euler's phi function or simply the phi function before Sylvester came up with the term \"totient\" for the function."@en . . "The function is usually denoted as \u03C6(n), a notation Gauss found after Euler formulated the function. It was first introduced as Euler's phi function or simply the phi function before Sylvester came up with the term \"totient\" for the function."@en . "Euler's totient function"@en . .