OFFSET
0,3
COMMENTS
Previous name was: A simple grammar.
LINKS
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 760
FORMULA
From Paul D. Hanna, Aug 28 2008: (Start)
E.g.f. satisfies: A(x*(1 + log(1-x))) = 1/(1 + log(1-x)).
E.g.f. satisfies: A(x) = 1/(1 + log(1 - x*A(x))).
E.g.f.: A(x) = (1/x)*Series_Reversion[x + x*log(1-x)]. (End)
a(n)=sum(k=0..n, binomial(n+k,n)*k!*sum(j=0..k, (-1)^(n+j)/(k-j)!*sum(i=0..j, stirling1(n,j-i)/i!)))/(n+1); [Vladimir Kruchinin, May 09 2013]
a(n) ~ n^(n-1) * c^n / (sqrt(1+c) * exp(n) * (c-1)^(2*n+1)), where c = LambertW(exp(2)) = 1.5571455989976114... - Vaclav Kotesovec, Jan 08 2014
a(n) = (1/(n+1)!) * Sum_{k=0..n} (n+k)! * |Stirling1(n,k)|. - Seiichi Manyama, Nov 06 2023
EXAMPLE
E.g.f.: A(x) = 1 + x + 5*x^2/2! + 47*x^3/3! + 660*x^4/4! +... [Paul D. Hanna, Aug 28 2008]
MAPLE
spec := [S, {C=Cycle(B), S=Sequence(C), B=Prod(S, Z)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
MATHEMATICA
CoefficientList[1/x*InverseSeries[Series[x + x*Log[1-x], {x, 0, 20}], x], x] * Range[0, 19]! (* Vaclav Kotesovec, Jan 08 2014 *)
PROG
(PARI) a(n)=n!*polcoeff((1/x)*serreverse(x+x*log(1-x +x*O(x^n))), n) \\ Paul D. Hanna, Aug 28 2008
(Maxima) a(n):=sum(binomial(n+k, n)*k!*sum((-1)^(n+j)/(k-j)!*sum(stirling1(n, j-i)/i!, i, 0, j), j, 0, k), k, 0, n)/(n+1); /* Vladimir Kruchinin, May 09 2013 */
CROSSREFS
KEYWORD
easy,nonn,changed
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
EXTENSIONS
New name using e.g.f., Vaclav Kotesovec, Jan 08 2014
STATUS
approved