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A054931
Number of unlabeled connected graphs up to complementarity.
2
1, 0, 0, 1, 5, 34, 331, 4949, 123764, 5713987, 497201633, 81514244540, 25084892188043, 14476409634230317, 15684138157859087576, 31969052260961397580693, 122903899605317560183278680, 893542862676093238616261481156, 12317116802837365393131147013965260
OFFSET
1,5
LINKS
V. A. Liskovets, Some easily derivable sequences, J. Integer Sequences, 3 (2000), #00.2.2.
FORMULA
a(n) = A001349(n) - (1/2)*A000088(n) + (1/2)*A000171(n). (see Eq. (4) in Liskovets) - Emeric Deutsch, Nov 18 2004
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 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, May 24 2000
EXTENSIONS
More terms from Emeric Deutsch, Nov 18 2004
Terms a(18) and beyond from Andrew Howroyd, Sep 17 2018
STATUS
approved