|
| |
|
|
A054935
|
|
Number of planar maps with n edges up to orientation-preserving duality.
|
|
0
| |
|
|
1, 3, 7, 33, 156, 1070, 7515, 59151, 483925, 4136964, 36416865, 329048627, 3037029030, 28553451498, 272766018806, 2642420298576, 25916954091582, 257009789443925
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,2
|
|
|
COMMENTS
| Replacing each edge by a vertex of degree 4, one sees that a(n) is also the number of non-isomorphic planar maps (a.k.a. clean dessins on the Riemann sphere) with n vertices of degree 4, and 2n edges.
|
|
|
LINKS
| V. A. Liskovets, Some easily derivable sequences, J. Integer Sequences, 3 (2000), #00.2.2.
|
|
|
FORMULA
| Average of A006384 and A006849 (the latter interspersed with 0's).
|
|
|
CROSSREFS
| Sequence in context: A057480 A051256 A057795 * A024496 A081890 A192880
Adjacent sequences: A054932 A054933 A054934 * A054936 A054937 A054938
|
|
|
KEYWORD
| nonn,easy,more
|
|
|
AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), May 24 2000
|
|
|
EXTENSIONS
| More terms from Valery A. Liskovets (liskov(AT)im.bas-net.by), May 27 2006
|
| |
|
|
