OFFSET
0,3
COMMENTS
Diagonal sums of Riordan array (1/(1-x), x/(1+x)), A112468.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..300
Index entries for linear recurrences with constant coefficients, signature (0,2,-1).
FORMULA
G.f.: (1+x)/((1-x)(1+x-x^2));
a(n) = Sum_{k=0..floor(n/2)} Sum_{j=0..n-2k} C(n-k-j-1, n-2k-j)*(-1)^(n-j).
MAPLE
a[0]:=1:a[1]:=1:a[2]:=2:a[3]:=1:for n from 4 to 50 do a[n]:=2*a[n-2]-a[n-3] od: seq(a[n], n=0..42); # Zerinvary Lajos, Apr 04 2008
MATHEMATICA
Accumulate[Table[(-1)^n Fibonacci[n-1], {n, 0, 50}]] (* Harvey P. Dale, Nov 05 2011 *)
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Paul Barry, Sep 06 2005
STATUS
approved