A054931 Number of unlabeled connected graphs up to complementarity.

1, 0, 0, 1, 5, 34, 331, 4949, 123764, 5713987, 497201633, 81514244540, 25084892188043, 14476409634230317, 15684138157859087576, 31969052260961397580693, 122903899605317560183278680, 893542862676093238616261481156, 12317116802837365393131147013965260

Offset: 1

Author

N. J. A. Sloane, May 24 2000

Keywords

• nonn
• easy

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..50
• V. A. Liskovets, Some easily derivable sequences, J. Integer Sequences, 3 (2000), #00.2.2.

Crossrefs

Cf. A001349, A000088, A000171.

Programs

Mathematica

A001349 = Cases[Import["https://oeis.org/A001349/b001349.txt", "Table"], {, }][[All, 2]];
A000088 = Cases[Import["https://oeis.org/A000088/b000088.txt", "Table"], {, }][[All, 2]];
A000171 = Cases[Import["https://oeis.org/A000171/b000171.txt", "Table"], {, }][[All, 2]];
a[n_] := A001349[[n+1]] - (1/2) A000088[[n+1]] + (1/2) A000171[[n]];
Array[a, 50] (* Jean-François Alcover, Aug 26 2019 *)

Formula

a(n) = A001349(n) - (1/2)*A000088(n) + (1/2)*A000171(n). (see Eq. (4) in Liskovets) - Emeric Deutsch, Nov 18 2004

Extensions

More terms from Emeric Deutsch, Nov 18 2004

Terms a(18) and beyond from Andrew Howroyd, Sep 17 2018