OFFSET
1,1
LINKS
Nathaniel Johnston, Table of n, a(n) for n = 1..5000
FORMULA
a(n) = A005117(n+1)^6. - Nathaniel Johnston, Jun 21 2011
Sum_{n>=1} 1/a(n) = zeta(6)/zeta(12) - 1 = A269404 - 1. - Amiram Eldar, Oct 13 2020
MAPLE
for n from 2 to 100 do if(numtheory[issqrfree](n))then printf("%d, ", n^6): fi: od: # Nathaniel Johnston, Jun 21 2011
MATHEMATICA
Select[ Range@37^6, Union[Last /@ FactorInteger@# ] == {6} &] (* Robert G. Wilson v *)
Select[Range[2, 37], SquareFreeQ]^6 (* Amiram Eldar, Oct 13 2020 *)
PROG
(Python)
from math import isqrt
from sympy import mobius
def A113851(n):
def f(x): return int(n+1-sum(mobius(k)*(x//k**2) for k in range(2, isqrt(x)+1)))
m, k = n, f(n)
while m != k: m, k = k, f(k)
return m**6 # Chai Wah Wu, Feb 25 2025
CROSSREFS
KEYWORD
easy,nonn,changed
AUTHOR
Cino Hilliard, Jan 25 2006
EXTENSIONS
More terms from Robert G. Wilson v, Jan 26 2006
STATUS
approved