OFFSET
1,2
COMMENTS
The circular maps are also the maps whose faces could be colored in two colors.
LINKS
M. A. Deryagina and A. D. Mednykh, On the enumeration of circular maps with given number of edges, Siberian Mathematical Journal, 54, No. 6, 2013, 624-639.
M. Deryagina, On the enumeration of hypermaps which are self-equivalent with respect to reversing the colors of vertices, Preprint 2016.
FORMULA
See formula for C(n) in Theorem 2.1 of Deryagina and Mednykh (2013).
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Dec 28 2013, based on email from Madina Deryagina and Alexander Mednykh.
STATUS
approved