OFFSET
0,7
COMMENTS
Previous name was: A simple grammar.
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..449
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 757
FORMULA
E.g.f.: x^4*log(-1/(-1+x))^2.
Recurrence: a(1)=0, a(2)=0, a(4)=0, a(3)=0, a(5)=0, a(6)=720, (-5*n^3+n^4+32*n-6*n^2+32)*a(n)+(9*n^2+5*n-2*n^3-42)*a(n+1)+(n^2-5*n+6)*a(n+2) = 0.
a(n) ~ (n-1)! * 2*(log(n) + gamma), where gamma is Euler-Mascheroni constant (A001620). - Vaclav Kotesovec, Oct 01 2013
a(n) = n*A052766(n-1) = 2*4!*binomial(n,4)*abs(Stirling1(n-4,2)) for n >= 4. - Andrew Howroyd, Aug 08 2020
MAPLE
spec := [S, {B=Cycle(Z), S=Prod(Z, Z, Z, Z, B, B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
MATHEMATICA
CoefficientList[Series[x^4*(Log[1-x])^2, {x, 0, 20}], x]* Range[0, 20]! (* Vaclav Kotesovec, Oct 01 2013 *)
PROG
(PARI) x='x+O('x^30); concat(vector(6), Vec(serlaplace(x^4*(log(1-x))^2))) \\ G. C. Greubel, Sep 05 2018
(PARI) a(n)={if(n>=4, 2*4!*binomial(n, 4)*abs(stirling(n-4, 2, 1)), 0)} \\ Andrew Howroyd, Aug 08 2020
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
EXTENSIONS
New name using e.g.f., Vaclav Kotesovec, Oct 01 2013
STATUS
approved