OFFSET
0,2
LINKS
FORMULA
a(n) = 3^floor((n+1)/2)*(-1)^C(n+1,2).
Binomial transform is A128018.
E.g.f.: cos(sqrt(3)*x) - sqrt(3)*sin(sqrt(3)*x). - Stefano Spezia, Dec 31 2022
MATHEMATICA
CoefficientList[Series[(1 - 3x)/(1 + 3*x^2), {x, 0, 40}], x] (* Stefano Spezia, Dec 31 2022 *)
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Paul Barry, Feb 11 2007
STATUS
approved