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%I #14 Feb 26 2022 10:35:05
%S 1,2,15,334,18521,2293896,586774783,292184148320,270280183791969,
%T 447043237292379520,1280479639717884356831,6180626271969237488205312
%N Number of n X n binary matrices that contain no 2 X 2 zero submatrix.
%F E.g.f.: the diagonal of exp( Sum_B x^|lB| * y^|rB| / |Aut(B,lB,rB)| ), where B runs over connected squarefree bipartite graphs with ordered bipartitions, (lB,rB) is the bipartition of B, and Aut(B,lB,rB) is the group of automorphisms of B preserving its bipartition.
%Y Cf. A175564, A133791, A300749.
%K hard,more,nonn
%O 0,2
%A _Max Alekseyev_, Jul 03 2010
%E a(6)-a(8) from _Hiroaki Yamanouchi_, Aug 27 2014
%E a(9)-a(11) from _Max Alekseyev_, Feb 26 2022
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