OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
For n > 35, a(n) < 7n. Asymptotically, a(n) ~ kn with k = zeta(3)/(zeta(3)-1) = 5.949... . - Charles R Greathouse IV, Oct 16 2015 [Corrected by Amiram Eldar, Aug 31 2024]
Sum_{n>=1} 1/a(n)^s = 1 + zeta(s) - zeta(3*s) - zeta(s)/zeta(3*s), for s > 1. - Amiram Eldar, Aug 31 2024
MATHEMATICA
With[{m = 10}, Select[Complement[Range[m^3], Range[m]^3], AnyTrue[FactorInteger[#][[;; , 2]], #1 > 2 &] &]] (* Amiram Eldar, Aug 31 2024 *)
PROG
(PARI) is(n)=my(f=factor(n)[, 2]); f%3 && vecmax(f)>2 \\ Charles R Greathouse IV, Oct 16 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Sep 25 2002
STATUS
approved