A054936 - OEIS

A054936

Number of achiral planar maps on n nodes up to orientation-preserving isomorphisms.

2, 4, 14, 47, 184, 761, 3314, 14997, 69886, 333884, 1626998, 8067786, 40580084, 206734083, 1064666724, 5536480877, 29036188788

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OFFSET

1,1

COMMENTS

Likely the same as A006443. - R. J. Mathar, Oct 13 2008

LINKS

Table of n, a(n) for n=1..17.

V. A. Liskovets, Some easily derivable sequences, J. Integer Sequences, 3 (2000), #00.2.2.

FORMULA

a(n) = 2*A006385(n) - A006384(n). [Liskovets eq 3a] - R. J. Mathar, Oct 01 2011

MATHEMATICA

A[s_Integer] := With[{s6 = StringPadLeft[ToString[s], 6, "0"]}, Cases[ Import["https://oeis.org/A" <> s6 <> "/b" <> s6 <> ".txt", "Table"], {_, _}][[All, 2]]];

A006385 = A@006385;

A006384 = A@006384;

a[n_] := 2 A006385[[n + 1]] - A006384[[n + 1]];

a /@ Range[17] (* Jean-François Alcover, Feb 21 2020 *)

CROSSREFS

Sequence in context: A263742 A263743 A062868 * A006443 A152103 A102879

Adjacent sequences: A054933 A054934 A054935 * A054937 A054938 A054939

KEYWORD

nonn,more

AUTHOR

N. J. A. Sloane, May 24 2000

STATUS

approved