OFFSET
1,2
COMMENTS
For n >= 3, this is related to the enumeration of rooted simple planar maps with n edges.
See A329775 for another version. Presumably only one of the two versions is correct.
REFERENCES
Liu, Yanpei, On the enumeration of simple planar maps, RUTCOR Research Report #37-87, Nov. 1987, RUTCOR, Hill Center, Rutgers University, NJ. See (20).
Liu, Yanpei, An enumerating equation of simple planar maps with face partition, RUTCOR Research Report #38-87, Nov. 1987, RUTCOR, Hill Center, Rutgers University, NJ. See (22).
LINKS
Yanpei Liu, On functional equations arising from map enumerations, Discrete Mathematics 123.1-3 (1993): 93-109. See (4.16).
MAPLE
f:=m -> (1/m!)*add(4*(2*m+1)!*(2*m-i-4)!/(i!*(m-i-2)!*(2*m-i+1)), i=0..m-2);
[seq(f(m), m=1..40)];
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Nov 25 2019
STATUS
approved