10.18453/rosdok_id00005834 Grüttmüller, Martin Martin Grüttmüller http://d-nb.info/gnd/122522559 Roberts, Ian T. Ian T. Roberts D’Arcy, Sue Sue D’Arcy Egan, Judith Judith Egan University of Rostock, Institute of Mathematics 2005 510 Mathematics 2005 en https://purl.uni-rostock.de/rosdok/id00005834 urn:nbn:de:gbv:28-rosdok_id00005834-8 The minimum number of blocks having maximum size precisely four that are required to cover, exactly λ times, all pairs of elements from a set of cardinality v is denoted by gλ(4)(v) are known except for λ = 1 andv = 17 or 18. It is known that 30<= g(4)(17) <= 31 and 32 <= g(4)(18) <= 33. In this paper we Show that g(4)(17) =/ 30 and g(4)(18) =/ 32, thus finalising the Determination of gλ(4)(v) for all λ and v