decompwlj 3D

Primes of the form 4x^2 + 25y^2

A107218 on the OEIS · family quadratic form

Weight–level plate of Primes of the form 4x^2 + 25y^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 viewerA107218 on the OEIS
Terms100,000 (n = 1 … 100,000)
Decomposable (a > 2d)99,999
Level class, k > L41,691 · 41.69 %
Weight class, k ≤ L58,308 · 58.31 %
Ties, k = L11
On the level line L = 110,330
Forced level, l ≤ d²171
Range of a(n)29 … 12,203,929
Range of the jump d8 … 1,240
Largest weight k, level L12,203,449, 1,355,257

155 different gaps occur, from 8 to 1,240; the level share is 41.69 %.

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.