OFFSET
0,2
FORMULA
G.f.: 8*(1-x)/(1+sqrt(1+4*x-4*x^2))^3.
PROG
(PARI) {a(n)=polcoeff(8*(1-x)/(1+sqrt(1+4*x-4*x^2+x*O(x^n)))^3, n)}
CROSSREFS
KEYWORD
sign
AUTHOR
Paul D. Hanna, Dec 27 2004
STATUS
approved