OFFSET
1,2
LINKS
Evgeniy Krasko, Alexander Omelchenko, Enumeration of 4-regular one-face maps, European Journal of Combinatorics, Volume 62, 2017, Pages 167-177.
FORMULA
a(g) = 2*((4g-2)!)/((4^g)*(g!)*((g-1)!)).
EXAMPLE
On a torus (g=1) there exists only one 4-regular one-face map.
CROSSREFS
KEYWORD
nonn
AUTHOR
Evgeniy Krasko, Sep 03 2017
STATUS
approved