For permutations avoiding consecutive patterns from a given set, we present a
combinatorial formula for the multiplicative inverse of the corresponding
exponential generating function. The formula comes from homological algebra
considerations in the same sense as the corresponding inversion formula for
avoiding word patterns comes from the well known Anick's resolution.
In many different settings (associative algebras, commutative algebras,
operads, dioperads), it is possible to develop the machinery of Gr\"obner
bases; it allows to find a "monomial replacement" for every object in the
corresponding category. The main goal of this article is to demonstrate how
this machinery can be used for the purposes of homological algebra. More
precisely, we define combinatorial resolutions in the monomial case and then
show how they can be adjusted to be used in the general homogeneous case. We
also discuss a way to make our monomial resolutions minimal.
We define a new monoidal category on collections (shuffle composition).
Monoids in this category (shuffle operads) turn out to bring a new insight in
the theory of symmetric operads. For this category, we develop the machinery of
Gr\"obner bases for operads, and present operadic versions of Bergman's Diamond
Lemma and Buchberger's algorithm. This machinery can be applied to study
symmetric operads. In particular, we obtain an effective algorithmic version of
Hoffbeck's PBW criterion of Koszulness for (symmetric) quadratic operads.
We define a new monoidal category on collections (shuffle composition).
Monoids in this category (shuffle operads) turn out to bring a new insight in
the theory of symmetric operads. For this category, we develop the machinery of
Gr\"obner bases for operads, and present operadic versions of Bergman's Diamond
Lemma and Buchberger's algorithm. This machinery can be applied to study
symmetric operads. In particular, we obtain an effective algorithmic version of
Hoffbeck's PBW criterion of Koszulness for (symmetric) quadratic operads.