OFFSET
0,4
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..200
FORMULA
E.g.f.: (exp(x)-1)*(exp(x^2/2)-1)*exp(-x - x^2/2)/(1-x).
a(n) ~ n! * (exp(1)-1)*(exp(1/2)-1)*exp(-3/2) = n! * 0.248720059264354... - Vaclav Kotesovec, Aug 07 2013
EXAMPLE
a(3) = 3: 132, 213, 321.
a(4) = 6: 1243, 1324, 1432, 2134, 3214, 4231.
MATHEMATICA
nn=22; Range[0, nn]!CoefficientList[Series[(Exp[x]-1)(Exp[x^2/2]-1)Exp[-x-x^2/2]/(1-x), {x, 0, nn}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Geoffrey Critzer, Feb 14 2013
STATUS
approved