The Markov numbers occur in solutions to the Diophantine Equation

and are related to Lagrange Numbers by

The first few solutions are , (1, 1, 2), (1, 2, 5), (1, 5, 13), (2, 5, 29), .... The solutions can be arranged in an infinite tree with two smaller branches on each trunk. It is not known if two different regions can have the same label. Strangely, the regions adjacent to 1 have alternate Fibonacci Numbers 1, 2, 5, 13, 34, ..., and the regions adjacent to 2 have alternate Pell Numbers 1, 5, 29, 169, 985, ....

Let be the number of Triples with
, then

where (Guy 1994, p. 166).

**References**

Conway, J. H. and Guy, R. K. *The Book of Numbers.* New York: Springer-Verlag, pp. 187-189, 1996.

Guy, R. K. ``Markoff Numbers.'' §D12 in
*Unsolved Problems in Number Theory, 2nd ed.* New York: Springer-Verlag, pp. 166-168, 1994.

© 1996-9

1999-05-26