Carmichael's totient function conjecture

This conjecture asserts that there exist natural numbers m, n, m≠n, for which $\varphi (m)=\varphi (n)$, where $\varphi ()$ denotes the Euler's totient function.

References

• Weisstein, Eric W. "Carmichael's Totient Function Conjecture." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/CarmichaelsTotientFunctionConjecture.html