Conjunctive Sequences (noch nicht übersetzt)

Problem 774

Let '$\&$' denote the bitwise AND operation.
For example, $10\,\&\, 12 = 1010_2\,\&\, 1100_2 = 1000_2 = 8$.

We shall call a finite sequence of integers $(a_1, a_2, \ldots, a_n)$ conjunctive if $a_i\,\&\, a_{i+1} \neq 0$ for all $i=1\ldots n-1$.

Define $c(n,b)$ to be the number of conjunctive sequences of length $n$ in which all terms are $\le b$.

You are given that $c(3,4)=18$, $c(10,6)=2496120$, and $c(100,200) \equiv 268159379 \pmod {998244353}$.

Find $c(123,123456789)$. Give your answer modulo $998244353$.