decompwlj 3D

Primes p such that 5*p + 4 is also prime

A023218 on the OEIS · family primes

Weight–level plate of Primes p such that 5*p + 4 is also prime
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 viewerA023218 on the OEIS
Terms100,000 (n = 1 … 100,000)
Decomposable (a > 2d)99,994
Level class, k > L45,500 · 45.50 %
Weight class, k ≤ L54,494 · 54.50 %
Ties, k = L0
On the level line L = 117,016
Forced level, l ≤ d²151
Range of a(n)3 … 14,901,743
Range of the jump d2 … 1,848
Largest weight k, level L14,900,777, 2,128,565

211 different gaps occur, from 2 to 1,848; the level share is 45.50 %; L = 1 holds 37 % of the level class; there are no ties; 6 terms do not decompose.

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.