  Inversion sequences of length $n$ are integer sequences $e_1,\ldots ,e_n$
with $0\le e_i<i$ for all $i$, which are in bijection with the permutations of
length $n$. In this paper, we classify all Wilf equivalence classes of
pattern-avoiding inversion sequences of length-4 patterns except for one case
(whether 3012 $\equiv$ 3201) and enumerate some of the length-4
pattern-avoiding inversion sequences that are in the OEIS.
