OFFSET
0,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
FORMULA
a(n) = a(n-2) - (n-3)*a(n-3), with a(0)=0, a(1)=1, a(2)=2. - G. C. Greubel, Oct 04 2019
MAPLE
a:= proc(n) option remember;
if n < 3 then n
else a(n-2)-(n-3)*a(n-3)
fi;
end proc:
seq(a(n), n = 0..35); # G. C. Greubel, Oct 04 2019
MATHEMATICA
a[0]=0; a[1]=1; a[2]=2; a[n_]:= a[n]= a[n-2] - (n-3)*a[n-3]; Table[a[n], {n, 0, 35}]
PROG
(PARI) my(m=35, v=concat([0, 1, 2], vector(m-3))); for(n=4, m, v[n] = v[n-2] - (n-4)*v[n-3] ); v \\ G. C. Greubel, Oct 04 2019
(Magma) I:=[0, 1, 2]; [n le 3 select I[n] else Self(n-2) - (n-4)*Self(n-3): n in [1..35]]; // G. C. Greubel, Oct 04 2019
(Sage)
def a(n):
if n<3: return n
else: return a(n-2) - (n-3)*a(n-3)
[a(n) for n in (0..35)] # G. C. Greubel, Oct 04 2019
(GAP) a:=[0, 1, 2];; for n in [4..35] do a[n]:=a[n-2]-(n-4)*a[n-3]; od; a; # G. C. Greubel, Oct 04 2019
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Roger L. Bagula, Sep 13 2006
EXTENSIONS
Edited by N. J. A. Sloane, Sep 17 2006
More terms from Max Alekseyev, Sep 13 2009
STATUS
approved