|
|
A054939
|
|
Number of connected labeled graphs with n nodes and an even number of edges.
|
|
1
|
|
|
1, 0, 3, 16, 376, 13292, 933488, 125771776, 33148165696, 17248244115968, 17820828776291072, 36677298103363352704, 150636101324832283976704, 1235824405515221864531935232, 20263840468865240117348466818048, 664289479167891600504168839585529856
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,3
|
|
LINKS
|
|
|
FORMULA
|
|
|
MATHEMATICA
|
nn = 15; Clear[f]; f[z_] := Sum[(1 + u)^Binomial[n, 2] z^n/n!, {n, 0, nn + 1}]; Drop[Map[Total[#[[1 ;; Binomial[nn, 2] ;; 2]]] &, Range[0, nn]! CoefficientList[Series[ Log[f[z]] , {z, 0, nn}], {z, u}]], 1] (* Geoffrey Critzer, Jul 27 2016 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|