OFFSET
0,4
COMMENTS
Diagonal sums of Riordan array (1-x-2x^2,x(1-x)), A109246.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (0,1,-1).
FORMULA
a(n) = a(n-2) - a(n-3), starting 1, -1, -1.
MATHEMATICA
a[0] = 1; a[1] = -1; a[2] = -1; a[n_] := a[n - 2] - a[n - 3]; Table[a[n], {n, 0, 50}] (* Wesley Ivan Hurt, Mar 06 2014 *)
CoefficientList[Series[(1 - x - 2 x^2)/(1 - x^2 + x^3), {x, 0, 40}], x] (* Vincenzo Librandi. Mar 12 2014 *)
LinearRecurrence[{0, 1, -1}, {1, -1, -1}, 60] (* Harvey P. Dale, Jun 03 2014 *)
PROG
(Magma) I:=[1, -1, -1, -2, 0, -1]; [n le 6 select I[n] else Self(n-2)-Self(n-3): n in [1..60]]; // Vincenzo Librandi, Mar 12 2014
(PARI) Vec((1-x-2*x^2)/(1-x^2+x^3) + O(x^50)) \\ Michel Marcus, Sep 17 2016
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Paul Barry, Jun 23 2005
STATUS
approved