A175563 Number of n X n binary matrices that contain no 2 X 2 zero submatrix.

1, 2, 15, 334, 18521, 2293896, 586774783, 292184148320, 270280183791969, 447043237292379520, 1280479639717884356831, 6180626271969237488205312

Offset

0,2

Links

Table of n, a(n) for n=0..11.

Formula

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.

Crossrefs

Cf. A175564, A133791, A300749.

Sequence in context: A030642 A365358 A297077 * A231443 A068391 A215743

Adjacent sequences: A175560 A175561 A175562 * A175564 A175565 A175566

Keyword

hard,more,nonn

Author

Max Alekseyev, Jul 03 2010

Extensions

a(6)-a(8) from Hiroaki Yamanouchi, Aug 27 2014

a(9)-a(11) from Max Alekseyev, Feb 26 2022

Status

approved