OFFSET
1,2
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Odd Powers.
FORMULA
a(n) ~ n^3. - Charles R Greathouse IV, Apr 20 2015
Sum_{n>=1} 1/a(n) = 1 + Sum_{k>=1} mu(2*k+1)*(1-zeta(2*k+1)) = 1.2479294392... - Amiram Eldar, Dec 21 2020
MAPLE
N:= 10^6: # to get all terms <= N
{1, seq(seq(a^(2*k+1), k = 1 .. floor((log[a](N)-1)/2)), a=2..floor(N^(1/3)))};
# if using Maple 11 or earlier, uncomment the next line
# sort(convert(%, list)); # Robert Israel, Apr 24 2015
MATHEMATICA
nn = 27000; Join[{1}, Union[Flatten[Table[n^i, {i, Prime[Range[2, PrimePi[Log[2, nn]]]]}, {n, 2, nn^(1/i)}]]]] (* T. D. Noe, Apr 19 2011 *)
PROG
(PARI) is(x)=p=ispower(x); x==1||(p>1&bitand(p, p-1)!=0) \\ Charles R Greathouse IV, Apr 20 2015; corrected by Jeppe Stig Nielsen, Jul 14 2015
(PARI) list(lim)=my(v=List([1])); forstep(e=3, log(lim)\log(2), 2, for(n=2, sqrtnint(lim\1, e), listput(v, n^e))); Set(v) \\ Charles R Greathouse IV, Apr 20 2015
(Python)
from sympy import mobius, integer_nthroot
def A070265(n):
def f(x): return int(n-2+x+sum(mobius(k)*(integer_nthroot(x, k)[0]-1) for k in range(3, x.bit_length(), 2)))
kmin, kmax = 1, 2
while f(kmax) >= kmax:
kmax <<= 1
while True:
kmid = kmax+kmin>>1
if f(kmid) < kmid:
kmax = kmid
else:
kmin = kmid
if kmax-kmin <= 1:
break
return kmax # Chai Wah Wu, Aug 14 2024
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Eric W. Weisstein, May 07 2002
EXTENSIONS
Name clarified by Charles R Greathouse IV, Oct 16 2015
STATUS
approved