decompwlj 3D

Cubefree numbers: numbers that are not divisible by any cube > 1

A004709 on the OEIS · family multiplicative · also known as Cubefree numbers

Weight–level plate of Cubefree numbers: numbers that are not divisible by any cube > 1
Click the plate to explore it in 3-D. Weight k across, level L up, both on log scales: blue in the weight class (k ≤ L), orange in the level class (k > L). The dashed diagonal is k = L.
Open in the 3-D viewerA004709 on the OEIS
Terms100,000 (n = 1 … 100,000)
Decomposable (a > 2d)99,998
Level class, k > L10,160 · 10.16 %
Weight class, k ≤ L89,838 · 89.84 %
Ties, k = L60
On the level line L = 110,103
Forced level, l ≤ d²0
Range of a(n)1 … 120,203
Range of the jump d1 … 5
Largest weight k, level L120,193, 60,100

No cube > 1 divides n. Density 1/zeta(3) = 0.83. The level share is 10.16 %; L = 1 holds 99 % of the level class.

The decomposition

Every term of a strictly increasing sequence is written a(n) = k(n)·L(n) + d(n): the jump d = a(n+1) − a(n), the weight k the least divisor of a − d greater than d, the level L = (a − d)/k. A term decomposes when a > 2d; it is in the level class when k > L and in the weight class when k ≤ L. See decompwlj.com and arXiv:0711.0865, or how it works, with worked examples and a live one.