A064524 Number of noncubes <= n.

0, 0, 1, 2, 3, 4, 5, 6, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 60, 61, 62, 63, 64, 65, 66, 67, 68

Offset: 0

Author

Reinhard Zumkeller, Oct 07 2001

Keywords

• nonn

Links

• Chai Wah Wu, Table of n, a(n) for n = 0..10000 (terms 0..1000 from Harry J. Smith)

Crossrefs

Cf. A007412, A048766.

Programs

PARI

a(n) = n - sqrtnint(n, 3); \\ Michel Marcus, Jun 18 2024

Python

from sympy import integer_nthroot
def A064524(n): return n-integer_nthroot(n,3)[0] # Chai Wah Wu, Jun 18 2024

Formula

a(n) = n - floor(CubicRoot(n)) = n-A048766(n).

G.f.: x/(1 - x)^2 - (1/(1 - x))*Sum_{k>=1} x^(k^3). - Ilya Gutkovskiy, Feb 16 2017