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.

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A334546 Array read by antidiagonals: T(n,k) is the number of unlabeled connected loopless multigraphs with n nodes of degree k or less.

Original entry on oeis.org

1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 2, 0, 0, 1, 1, 3, 2, 0, 0, 1, 1, 4, 4, 2, 0, 0, 1, 1, 5, 9, 12, 2, 0, 0, 1, 1, 6, 14, 37, 22, 2, 0, 0, 1, 1, 7, 23, 93, 146, 68, 2, 0, 0, 1, 1, 8, 32, 203, 602, 772, 166, 2, 0, 0, 1, 1, 9, 46, 399, 2126, 5847, 4449, 534, 2, 0, 0
Offset: 0

Views

Author

Andrew Howroyd, May 05 2020

Keywords

Comments

This sequence may be derived from A333893 by inverse Euler transform.

Examples

			Array begins:
==============================================
n\k | 0 1 2   3    4     5      6       7
----+-----------------------------------------
  0 | 1 1 1   1    1     1      1       1 ...
  1 | 1 1 1   1    1     1      1       1 ...
  2 | 0 1 2   3    4     5      6       7 ...
  3 | 0 0 2   4    9    14     23      32 ...
  4 | 0 0 2  12   37    93    203     399 ...
  5 | 0 0 2  22  146   602   2126    6308 ...
  6 | 0 0 2  68  772  5847  34126  164965 ...
  7 | 0 0 2 166 4449 66289 716141 6021463 ...
  ...
		

Crossrefs

Columns k=3..5 are A243391, A289157, A334547.
Main diagonal is A334546.
Cf. A289987, A328682 (regular), A333893 (not necessarily connected).

Formula

Column k is the inverse Euler transform of column k of A333893.

A289988 Number of unlabeled connected loopless multigraphs with n nodes of degree n or less.

Original entry on oeis.org

1, 1, 2, 4, 37, 602, 34126, 6021463, 3616906549, 7361925161868, 51324462383008758, 1240420936122453106498, 105141919479926837860474091, 31581183353539008502807807352728
Offset: 0

Views

Author

Natan Arie Consigli, Aug 19 2017

Keywords

Comments

Multigraphs are loopless.

Crossrefs

Main diagonal of A334546.

Programs

  • nauty
    for n in {1..8}; do geng -c -D${n} ${n} -q | multig -m$[${n}-1] -D$[${n}-1] -u; done

Extensions

a(0) corrected and a(9)-a(13) from Andrew Howroyd, May 05 2020
Showing 1-2 of 2 results.