OFFSET
0,2
EXAMPLE
G.f.: A(x) = 1 + 6*x - 36*x^2 + 216*x^3 - 2592*x^4 + 23328*x^5 +...
where
A(x)^2 = 1 + 12*x - 36*x^2 - 1296*x^4 - 108864*x^6 - 12317184*x^8 +...
A(x)^3 = 1 + 18*x - 432*x^3 - 23328*x^5 - 2239488*x^7 - 272097792*x^9 +...
PROG
(PARI) {a(n)=local(A=[1, 6]); for(k=2, n, A=concat(A, 0); if(k%2==1, A[#A]=-Vec(Ser(A)^2)[#A]/2, A[#A]=-Vec(Ser(A)^3)[#A]/3)); A[n+1]}
CROSSREFS
KEYWORD
sign
AUTHOR
Paul D. Hanna, Oct 06 2011
STATUS
approved