|
|
A241795
|
|
Number of ballot sequences of length n having exactly two descents.
|
|
2
|
|
|
3, 21, 101, 373, 1174, 3337, 8642, 21148, 48713, 108147, 229984, 476430, 955667, 1879169, 3603751, 6801106, 12584048, 22974152, 41268291, 73301654, 128441712, 222871187, 382322022, 650209758, 1094918922, 1829777544, 3031447986, 4987910871, 8144753275
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
5,1
|
|
LINKS
|
|
|
EXAMPLE
|
a(5) = 3: [1,2,1,2,1], [1,2,1,3,1], [1,2,1,3,2].
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|