OFFSET
0,3
FORMULA
G.f.: g/(1-f) where f/(1-f)^4=x and g=1/(1-f); a(n)=(-1)^n*sum{k=0..floor(n/2), ((4k+1)/(3n-2k+1))*binomial(4n-4k, n-2k)}.
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Paul Barry, Jul 06 2005
STATUS
approved