OFFSET
0,3
FORMULA
G.f.: A(x) = (1/x)*series_reversion[x*Sum_{n>=0} x^n/2^(n*(n-1)/2)].
EXAMPLE
A(x) = 1 - x + 3/2*x^2 - 21/8*x^3 + 319/64*x^4 - 10193/1024*x^5 +...
1 = A(x) + A(x)^2*x + A(x)^3*x^2/2 + A(x)^4*x^3/8 + A(x)^5*x^4/64 + ...
PROG
(PARI) {a(n)=2^(n*(n+1)/2)*polcoeff((1/x)*serreverse(sum(k=1, n+1, x^k/2^(k*(k-1)/2))+O(x^(n+2))), n)}
CROSSREFS
KEYWORD
sign
AUTHOR
Paul D. Hanna, Nov 23 2007
STATUS
approved