OFFSET
0,3
COMMENTS
E.g.f. satisfies (1-x)*f'(x) = (1+x+x^2)*f(x).
FORMULA
a(n) ~ n!*exp(-5/2)*n^2/2. - Vaclav Kotesovec, Jun 27 2013
D-finite with recurrence a(n) -n*a(n-1) +(-n+1)*a(n-2) -(n-1)*(n-2)*a(n-3)=0. - R. J. Mathar, Aug 20 2021
MAPLE
read transforms; Order:=25; ics:=f(0)=1;
e1:=(1-x)*diff(f(x), x) = (1+x+x^2)*f(x);
dsolve({e1, ics}, f(x), series);
SERIESTOLISTMULT(rhs(%));
MATHEMATICA
CoefficientList[Series[E^(-x*(x+4)/2)/(1-x)^3, {x, 0, 20}], x]* Range[0, 20]! (* Vaclav Kotesovec, Jun 27 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Aug 12 2011
STATUS
approved