decompwlj 3D

Numbers k for which sigma(k) < sigma(k+1)

A053224 on the OEIS · family divisor functions

Weight–level plate of Numbers k for which sigma(k) < sigma(k+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 viewerA053224 on the OEIS
Terms100,000 (n = 1 … 100,000)
Decomposable (a > 2d)99,997
Level class, k > L15,984 · 15.98 %
Weight class, k ≤ L84,013 · 84.02 %
Ties, k = L90
On the level line L = 114,957
Forced level, l ≤ d²1
Range of a(n)1 … 200,005
Range of the jump d1 … 4
Largest weight k, level L200,003, 99,996

The gaps are 1, 2, 3 and 4; the level share is 15.98 %; L = 1 holds 94 % 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.