We give an alternative proof of a conjecture of Bollobás, Brightwell and Leader, first proved by Peter Allen, stating that the number of Boolean functions definable by 2-SAT formulae is . One step in the proof determines the asymptotics of the number of ‘odd-blue-triangle-free’ graphs on n vertices.
(Received May 20 2008)
(Revised February 10 2009)
(Online publication June 01 2009)
† Supported by NSF grant DMS0701175.