OFFSET
0,5
FORMULA
E.g.f.: Sum_{k>=0} x^k / (k! * (1 + k*x)).
MATHEMATICA
Join[{1}, Table[n!*Sum[ (-k)^(n - k)/k!, {k, 0, n}], {n, 1, 20}]] (* Vaclav Kotesovec, May 28 2022 *)
PROG
(PARI) a(n) = n!*sum(k=0, n, (-k)^(n-k)/k!);
(PARI) my(N=20, x='x+O('x^N)); Vec(serlaplace(sum(k=0, N, x^k/(k!*(1+k*x)))))
(Python)
from math import factorial
def A354437(n): return sum(factorial(n)*(-k)**(n-k)//factorial(k) for k in range(n+1)) # Chai Wah Wu, May 28 2022
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, May 28 2022
STATUS
approved