A056156 - OEIS

A056156

Number of connected bipartite graphs with n edges, no isolated vertices and a distinguished bipartite block, up to isomorphism.

1, 2, 3, 7, 12, 32, 67, 181, 458, 1295, 3642, 10975, 33448, 106424, 345964, 1159489, 3975367, 13977808, 50238606, 184629655, 692757132, 2652892219, 10359676617, 41233344350, 167171988557, 690054189750, 2898637406813, 12385234548345

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

EULERi transform of A049311.

Also the number of non-isomorphic connected set multipartitions (multisets of sets) of weight n. The weight of a set multipartition is the sum of sizes of its parts. Weight is generally not the same as number of vertices. - Gus Wiseman, Sep 23 2018

LINKS

Jean-François Alcover, Table of n, a(n) for n = 1..102

Daniel R. Herber, Enhancements to the perfect matching approach for graph enumeration-based engineering challenges, Proceedings of the ASME 2020 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference (IDETC/CIE 2020).

N. J. A. Sloane, Transforms

EXAMPLE

From Gus Wiseman, Sep 24 2018: (Start)

Non-isomorphic representatives of the a(1) = 1 through a(4) = 7 connected set multipartitions:

{{1},{1}} {{2},{1,2}} {{3},{1,2,3}}

{{1},{1},{1}} {{1,2},{1,2}}

{{1,3},{2,3}}

{{1},{2},{1,2}}

{{2},{2},{1,2}}

{{1},{1},{1},{1}}

(End)

MATHEMATICA

A049311 = Cases[Import["https://oeis.org/A049311/b049311.txt", "Table"], {_, _}][[All, 2]];

(* EulerInvTransform is defined in A022562 *)

EulerInvTransform[A049311] (* Jean-François Alcover, Mar 16 2020 *)

CROSSREFS

Cf. A007716, A007718, A056156, A319557, A319565, A319566.

Sequence in context: A305752 A034786 A080107 * A112837 A056355 A056356

Adjacent sequences: A056153 A056154 A056155 * A056157 A056158 A056159

KEYWORD

nonn

AUTHOR

Vladeta Jovovic, Jul 30 2000

EXTENSIONS

More terms from Max Alekseyev, Jul 22 2009

STATUS

approved