  A Steiner 2-design of block size k is an ordered pair (V, B) of finite sets
such that B is a family of k-subsets of V in which each pair of elements of V
appears exactly once. A Steiner 2-design is said to be r-even-free if for every
positive integer i =< r it contains no set of i elements of B in which each
element of V appears exactly even times. We study the even-freeness of a
Steiner 2-design when the cyclic group acts regularly on V. We prove the
existence of infinitely many nontrivial Steiner 2-designs of large block size
which have the cyclic automorphisms and higher even-freeness than the trivial
lower bound but are not the points and lines of projective geometry.
