OFFSET
1,1
FORMULA
G.f.: 2*x*(1+x-x^2)*(1-4*x+x^2)/((1-10*x+3*x^2)*(1-x)^2).
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Frans Clauwens (F.Clauwens(AT)science.ru.nl), Jun 09 2005
STATUS
approved