Noncototient

A Positive value of $n$ for which $x-\phi(x)=n$ has no solution, where $\phi(x)$ is the Totient Function. The first few are 10, 26, 34, 50, 52, ... (Sloane's A005278).

See also Nontotient, 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 A005278/M4688 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.