Kernel
210 · 213 · 216
Cosine sum over that triplet, with φc at 0° for constructive sign. A mathematical expression only.
Modular filter
- n3 ≡ 0, 1, 8 mod 9
- two cubes ≡ 0, 1, 2, 7, 8
- three cubes ≡ 0, 1, 2, 3, 6, 7, 8
- four cubes ≡ every residue
4 and 5 mod 9 cannot be a sum of three cubes. They can be a sum of four. That is the whole constraint.
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