|
|
A085110
|
|
a(1)=1, then add 1 multiply by 2 to get a(2), subtract 1 and multiply by 3 to get a(3), add 1 and multiply by 4 to get a(4) and so on.
|
|
1
|
|
|
1, 4, 9, 40, 195, 1176, 8225, 65808, 592263, 5922640, 65149029, 781788360, 10163248667, 142285481352, 2134282220265, 34148515524256, 580524763912335, 10449445750422048, 198539469258018893, 3970789385160377880, 83386577088367935459, 1834504695944094580120
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
LINKS
|
|
|
FORMULA
|
a(1)=1, a(n)=n*a(n-1)+(-1)^n*n ; a(n)=round(n!*(2-exp(-1)))+(-1)^n. - Benoit Cloitre, Sep 24 2006
a(n) = ((n-2)*n/(n-1))*a(n-1) + n*a(n-2). - Robert Israel, Aug 04 2014
|
|
MAPLE
|
a[1]:= 1:
for n from 2 to 30 do a[n]:= n*(a[n-1]+(-1)^n) od:
|
|
MATHEMATICA
|
nxt[{n_, a_}]:={n+1, If[OddQ[n], (n+1)(a+1), (n+1)(a-1)]}; Transpose[ NestList[ nxt, {1, 1}, 30]][[2]] (* Harvey P. Dale, Aug 04 2014 *)
|
|
PROG
|
(PARI) a(n)=if(n<2, 1, n*a(n-1)+(-1)^n*n) \\ Benoit Cloitre, Sep 24 2006
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|