|
|
A024420
|
|
a(n) = n! * Sum_{j=0..floor(n/2)} (-1)^j/binomial(n,j).
|
|
2
|
|
|
1, 1, 1, 4, 22, 108, 612, 4416, 36576, 331200, 3319200, 36806400, 445046400, 5813579520, 81716947200, 1230656716800, 19761225523200, 336973967769600, 6082189179494400, 115851849523200000, 2322322137354240000, 48869666136023040000
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,4
|
|
LINKS
|
|
|
MAPLE
|
a:= n-> n!*add((-1)^j/binomial(n, j), j=0..iquo(n, 2)):
|
|
MATHEMATICA
|
Table[n!*Sum[(-1)^k/Binomial[n, k], {k, 0, Floor[n/2]}], {n, 0, 20}] (* Vaclav Kotesovec, Jul 10 2019 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|