|
|
A089043
|
|
a(n) = n!^2 + (-1)^n.
|
|
1
|
|
|
0, 5, 35, 577, 14399, 518401, 25401599, 1625702401, 131681894399, 13168189440001, 1593350922239999, 229442532802560001, 38775788043632639999, 7600054456551997440001, 1710012252724199423999999, 437763136697395052544000001, 126513546505547170185215999999
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
p = 2*n+1 is prime iff it divides a(n) (Wilson's theorem) for instance let n=5, p =11 : a(5) = 14399 = 11*1309, so 11 is prime.
|
|
LINKS
|
|
|
FORMULA
|
a(n) = n^2*(a(n-1)-(-1)^(n-1))+(-1)^n.
|
|
EXAMPLE
|
a(5) = 14399 because 14399=(5!)^2+(-1)^5.
|
|
PROG
|
|
|
CROSSREFS
|
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
Serge Boisse (serge.boisse(AT)aviation-civile.gouv.fr), Dec 02 2003
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|