OFFSET
1,3
FORMULA
a(n) = Sum_{k=1..n-1} |Stirling1(n, k)|*a(k).
MATHEMATICA
Clear[a]; a[1] = 1; a[n_] := a[n] = Sum[Abs[StirlingS1[n, k]]*a[k], {k, 1, n-1}]; Table[a[n], {n, 1, 20}] (* Vaclav Kotesovec, May 29 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladeta Jovovic, Sep 14 2003
STATUS
approved