|
|
A054943
|
|
Number of connected oriented graphs on n nodes with an odd number of edges.
|
|
2
|
|
|
0, 2, 8, 320, 27584, 6991360, 5179178368, 11396324458496, 74944172892993536, 1476405354971707604992, 87208352627656970712229888, 15450530398306943408625302896640, 8211400756816955708062672318337859584
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
LINKS
|
|
|
FORMULA
|
|
|
MATHEMATICA
|
nn = 15; g[z] :=Sum[(1 + 2 u)^Binomial[n, 2] z^n/n!, {n, 0, nn}]; Drop[
Map[Total[#[[2 ;; Binomial[nn, 2] + 1 ;; 2]]]&, Range[0, nn]!CoefficientList[
|
|
PROG
|
(PARI) seq(n)={my(A=O(x*x^n)); Vec(serlaplace(log(sum(k=0, n, 3^binomial(k, 2)*x^k/k!) + A) - log(cos(x + A) + sin(x + A)))/2, -n)} \\ Andrew Howroyd, Sep 10 2018
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|