Let
be an increasing sequence of nonnegative integers such that every nonnegative integer can be expressed uniquely in the form
, where
and
are not necessarily distinct. Determine
.
%V0
Let $a_{0},a_{1},a_{2},\ldots$ be an increasing sequence of nonnegative integers such that every nonnegative integer can be expressed uniquely in the form $a_{i}+2a_{j}+4a_{k}$, where $i,j$ and $k$ are not necessarily distinct. Determine $a_{1998}$.
Školjka