OFFSET
0,11
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..450
FORMULA
a(n) = n! * (1 - Sum_{k=0..floor(n/10)} (-1)^k/(k!10^k));
a(n)/n! is asymptotic to 1-e^(-1/10).
E.g.f.: (1-exp(-x^10/10))/(1-x). - Alois P. Heinz, Oct 11 2017
Conjectures from Stéphane Rézel, Dec 11 2019: (Start)
Recurrence: a(n) = n*a(n-1), for n > 10 and n !== 0 (mod 10);
for k > 1, a(10*k) = a(10*k-1)*S(k)/S(k-1) where S(k) = 10*k*S(k-1) - (-1)^k with S(1) = 1.
(End)
PROG
(PARI) a(n) = n! * (1 - sum(k=0, floor(n/10), (-1)^k/(k!*10^k) ) ); \\ Stéphane Rézel, Dec 11 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved