decompwlj 3D

Numbers with 20 divisors

A030638 on the OEIS · family divisor functions

Weight–level plate of Numbers with 20 divisors
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 viewerA030638 on the OEIS
Terms100,000 (n = 1 … 100,000)
Decomposable (a > 2d)100,000
Level class, k > L25,857 · 25.86 %
Weight class, k ≤ L74,143 · 74.14 %
Ties, k = L5
On the level line L = 12,455
Forced level, l ≤ d²89
Range of a(n)240 … 7,136,368
Range of the jump d1 … 638
Largest weight k, level L7,135,001, 3,566,551

382 different gaps occur, from 1 to 638; the level share is 25.86 %.

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.