decompwlj 3D

Primes of the form 4x^2 + 5y^2

A106963 on the OEIS · family quadratic form

Weight–level plate of Primes of the form 4x^2 + 5y^2
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 viewerA106963 on the OEIS
Terms100,000 (n = 1 … 100,000)
Decomposable (a > 2d)99,997
Level class, k > L41,589 · 41.59 %
Weight class, k ≤ L58,408 · 58.41 %
Ties, k = L13
On the level line L = 110,186
Forced level, l ≤ d²158
Range of a(n)5 … 12,202,049
Range of the jump d8 … 1,380
Largest weight k, level L12,199,909, 1,354,777

152 different gaps occur, from 8 to 1,380; the level share is 41.59 %.

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.