Nontotient

A Positive Even value of $n$ for which $\phi(x)=n$, where $\phi(x)$ is the Totient Function, has no solution. The first few are 14, 26, 34, 38, 50, ... (Sloane's A005277).

See also Noncototient, Totient Function

References

Guy, R. K. Unsolved Problems in Number Theory, 2nd ed. New York: Springer-Verlag, p. 91, 1994.

Sloane, N. J. A. Sequence A005277/M4927 in ``An On-Line Version of the Encyclopedia of Integer Sequences.'' http://www.research.att.com/~njas/sequences/eisonline.html and Sloane, N. J. A. and Plouffe, S. The Encyclopedia of Integer Sequences. San Diego: Academic Press, 1995.