decompwlj 3D

Primes of the form 9*n^2 + 1

A156226 on the OEIS · family primes

Weight–level plate of Primes of the form 9*n^2 + 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 viewerA156226 on the OEIS
Terms100,000 (n = 1 … 100,000)
Decomposable (a > 2d)99,994
Level class, k > L99,994 · 100.00 %
Weight class, k ≤ L0 · 0.00 %
Ties, k = L0
On the level line L = 116,020
Forced level, l ≤ d²99,994
Range of a(n)37 … 40,789,093,849,957
Range of the jump d540 … 6,662,229,696
Largest weight k, level L40,773,997,238,473, 515,677

99,544 different gaps occur, from 540 to 6,662,229,696; every decomposable term is forced level (l <= d^2); 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.