  Motivated by a conjecture posed by Fulmek and Krattenthaler, we provide
product formulas for the number of lozenge tilings of a semiregular hexagon
containing a horizontal intrusion. As a direct corollary, we obtain a product
formula for the number of boxed plane partitions with a certain restriction. We
also investigate the asymptotic behavior of the ratio between the number of
lozenge tilings of a semiregular hexagon containing a horizontal intrusion and
that of a semiregular hexagon without an intrusion.
