Status: exploratory, archived. Not an OEIS submission.
This folder documents the p = 3 member of the power-balance family: the analogue, for sums of four cubes, of the four-square balance-gap record locations A396760 (the p = 2 case, the active sequence of this repository). It is retained for reference and reproducibility. If you use or extend these terms, please reference this repository.
For a representable integer N, write
N = a^3 + b^3 + c^3 + d^3, 0 <= a <= b <= c <= d (integers).
Let minmax(N) be the least possible largest part d over all such representations, and let lb(N) be the least integer m with 4*m^3 >= N. The balance gap is
g(N) = minmax(N) - lb(N).
a(n) is the n-th representable N, taken in increasing order, at which g(N) exceeds all earlier values. Unlike p = 2 (Lagrange), for p >= 3 not every integer is a sum of four p-th powers; records are taken over the representable N only.
1, 27, 218, 731, 1331, 2745, 4913, 6862, 10648, 15627, 21954, 27016, 35938,
46658, 54896, 68956, 85186, 97338, 117650, 140700, 166377, 185195, 216002,
250050, 274642
These 25 terms are complete for N <= 300000 (exhaustive scan); nothing is asserted beyond that bound. The corresponding record gaps are 0, 1, 2, …, 24: within the scanned range every record raises the gap by exactly 1, unlike p = 2, where the record gaps jump (0, 1, 2, 3, 4, 6, 9, …).
b-file.txt — the 25 verified terms, offset 1.program.gp — PARI/GP scanner: lista(Nmax) prints every record location <= Nmax.../../exploratory-src/balance_records.py — reference computation for the whole
p = 2..7 family.../../../viz/power-balance/ — interactive visualization of the family.