OFFSET
1,8
COMMENTS
First differ from A043281 at n = 49.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
Multiplicative with a(p^e) = 1 if e <= p, and a(p^e) = 2 if e > p.
a(n) >= 1, with equality if and only if n is in A207481.
Dirichlet g.f.: zeta(s) * Product_{p prime} (1 + 1/p^((p+1)*s)).
Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = Product_{p prime} (1 + 1/p^(p+1)) = 1.13896197534988330925... .
MATHEMATICA
f[p_, e_] := If[e <= p, 1, 2]; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100]
PROG
(PARI) a(n) = {my(f = factor(n)); prod(i = 1, #f~, if(f[i, 2] <= f[i, 1], 1, 2)); }
CROSSREFS
KEYWORD
nonn,easy,mult
AUTHOR
Amiram Eldar, Dec 21 2023
STATUS
approved