OFFSET
0,5
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,0,-2,-1).
FORMULA
a(n) = a(n-1) - 2*a(n-3) - a(n-4).
a(n) = Sum_{k=0..n} Sum_{j=0..n} C(j, n-j)*C(k, j-k)*(-1)^(j-k).
MATHEMATICA
LinearRecurrence[{1, 0, -2, -1}, {1, 1, 1, -1}, 40] (* James C. McMahon, Jun 07 2024 *)
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Paul Barry, Sep 09 2005
STATUS
approved