This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A175563 #14 Feb 26 2022 10:35:05 %S A175563 1,2,15,334,18521,2293896,586774783,292184148320,270280183791969, %T A175563 447043237292379520,1280479639717884356831,6180626271969237488205312 %N A175563 Number of n X n binary matrices that contain no 2 X 2 zero submatrix. %F A175563 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 A175563 Cf. A175564, A133791, A300749. %K A175563 hard,more,nonn %O A175563 0,2 %A A175563 _Max Alekseyev_, Jul 03 2010 %E A175563 a(6)-a(8) from _Hiroaki Yamanouchi_, Aug 27 2014 %E A175563 a(9)-a(11) from _Max Alekseyev_, Feb 26 2022