OFFSET
1,3
COMMENTS
For the reversion of x - a*x^2 - b*x^5 (a!=0, b!=0) we have a(n) = Sum_{j=0..floor((n-1)/3)} a^(n-4*j-1)*b^j*binomial(n-3*j-1,j)*binomial(2*n-3*j-2,n-1)/n, n > 0.
LINKS
Vladimir Kruchinin, The method for obtaining expressions for coefficients of reverse generating functions, arXiv:1211.3244 [math.CO], 2012.
FORMULA
a(n) = Sum_{j=0..floor((n-1)/3)} 2^j*binomial(n-3*j-1,j)*binomial(2*n-3*j-2,n-1)/n, n > 0.
PROG
(Maxima)
a(n):=sum(2^j*binomial(n-3*j-1, j)*binomial(2*n-3*j-2, n-1), j, 0, (n-1)/3)/n;
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Kruchinin, May 28 2011
STATUS
approved