cp's OEIS Frontend

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.

Showing 1-2 of 2 results.

A138347 Number of squarefree bipartite graphs on n vertices.

Original entry on oeis.org

1, 2, 3, 6, 10, 21, 39, 86, 182, 440, 1074, 2941, 8424, 26720, 90883, 340253, 1384567, 6186907, 30219769, 161763233, 946742190, 6054606722, 42229136988, 320741332093, 2648348712904
Offset: 1

Views

Author

Vladeta Jovovic, May 18 2008

Keywords

Links

Crossrefs

Cf. A006786, A300749.

Extensions

More terms from Brendan McKay, Feb 04 2013
One more term from Brendan McKay, Mar 11 2018

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

Original entry on oeis.org

1, 2, 15, 334, 18521, 2293896, 586774783, 292184148320, 270280183791969, 447043237292379520, 1280479639717884356831, 6180626271969237488205312
Offset: 0

Views

Author

Max Alekseyev, Jul 03 2010

Keywords

Crossrefs

Cf. A175564, A133791, A300749.

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.

Extensions

a(6)-a(8) from Hiroaki Yamanouchi, Aug 27 2014
a(9)-a(11) from Max Alekseyev, Feb 26 2022
Showing 1-2 of 2 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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