OFFSET
1,2
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 1..10000
FORMULA
Sum_{k=1..n} a(k) ~ 3*n.
Multiplicative with a(p) = 2, and a(p^e) = 3 - (e-2)*(p^2-1) for e >= 2. - Amiram Eldar, Sep 15 2023
MATHEMATICA
f[p_, e_] := 3 - (e-2)*(p^2-1); f[p_, 1] = 2; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Sep 15 2023 *)
PROG
(PARI) for(n=1, 100, print1(direuler(p=2, n, (1 - p^2*X^3)/(1-X)^2)[n], ", "))
CROSSREFS
KEYWORD
sign,easy,mult
AUTHOR
Vaclav Kotesovec, Dec 25 2022
STATUS
approved