OFFSET
1,2
LINKS
FORMULA
G.f. (1-x^2)*(1-x)^2/(1-3*x+x^2+3*x^3-3*x^4).
MATHEMATICA
CoefficientList[Series[(1-x^2)(1-x)^2/(1-3x+x^2+3x^3-3x^4), {x, 0, 40}], x] (* Harvey P. Dale, May 28 2017 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Ralf Stephan, Jul 06 2003
STATUS
approved