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

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