OFFSET
0,3
FORMULA
a(n) = numerator([x^n] exp(n*(exp(x)-1))). - Alois P. Heinz, Dec 07 2020
MAPLE
A:= proc(n, k) option remember; `if`(n=0, 1, (1+
add(binomial(n-1, j-1)*A(n-j, k), j=1..n-1))*k)
end:
a:= n-> numer(A(n$2)/n!):
seq(a(n), n=0..20); # Alois P. Heinz, Dec 07 2020
MATHEMATICA
a[n_] := BellB[n, n]/n! // Numerator;
Table[a[n], {n, 0, 20}] (* Jean-François Alcover, May 27 2022 *)
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
William C. Laursen, Dec 03 2020
STATUS
approved