  We prove the existence of a ternary sequence of factor complexity $2n+1$ for
any given vector of rationally independent letter frequencies. Such sequences
are constructed from an infinite product of two substitutions according to a
particular Multidimensional Continued Fraction algorithm. We show that this
algorithm is conjugate to a well-known one, the Selmer algorithm.
Experimentations (Baldwin, 1992) suggest that their second Lyapunov exponent is
negative which presages finite balance properties.
