OFFSET
1,3
FORMULA
a(n) = (1/2)*(-1)^n*A139086(n) for n>2 with a(1)=a(2)=1.
EXAMPLE
G.f.: A(x) = x + x^2 - 2*x^3 + 15*x^4 - 158*x^5 + 2058*x^6 -+...
Series_Reversion(A(x)) = x - x^2 + 4*x^3 - 30*x^4 + 316*x^5 -+...
which equals -G(-x) where G(x) = g.f. of A139086.
PROG
(PARI) {a(n)=local(A=x+x^2); if(n<1, 0, for(i=3, n+1, A=A-polcoeff(serreverse(A+x*O(x^i)), i)*x^i); polcoeff(A, n))}
CROSSREFS
KEYWORD
sign
AUTHOR
Paul D. Hanna, Apr 08 2008
STATUS
approved