  The operads of Poisson and Gerstenhaber algebras are generated by a single
binary element if we consider them as Hopf operads (i.e. as operads in the
category of cocommutative coalgebras). In this note we discuss in details the
Hopf operads generated by a single element of arbitrary arity. We explain why
the dual space to the space of $n$-ary operations in this operads are quadratic
and Koszul algebras. We give the detailed description of generators, relations
and a certain monomial basis in these algebras.
