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On a4+b4+c4+d4=(a+27(b+c+d))4 and ten other new infinite families
Abstract
In 2008, Jacobi and Madden proved that a4+b4+c4+d4=e4 has infinitely many primitive solutions with the linear relation e=a+b+c+d. We extend their result to relations with rational cubes e=a+k3(b+c+d) and prove infinitude for k=3 and $10$ other k≠ 1. We compile $30$ starting solutions. In the spirit of Jacobi and Madden's original paper, everything here is simple algebra except one theorem of Mazur.
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BibTeX
@misc{veselovac2026a4b4c4d4a27bcd4,
title = {{On $a^4+b^4+c^4+d^4=(a+27(b+c+d))^4$ and ten other new infinite families}},
author = {Matej Veselovac and Tito Piezas III},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.12181},
eprint = {2610.12181},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.12181},
}
RIS
TY - UNPB
TI - On a^4+b^4+c^4+d^4=(a+27(b+c+d))^4 and ten other new infinite families
AU - Matej Veselovac
AU - Tito Piezas III
PY - 2026
DA - 2026/10/08
PB - arXiv
DO - 10.48550/arxiv.2610.12181
UR - https://arxiv.org/abs/2610.12181
AB - In 2008, Jacobi and Madden proved that a^4+b^4+c^4+d^4=e^4 has infinitely many primitive solutions with the linear relation e=a+b+c+d. We extend their result to relations with rational cubes e=a+k^3(b+c+d) and prove infinitude for k=3 and $10$ other k≠ 1. We compile $30$ starting solutions. In the spirit of Jacobi and Madden's original paper, everything here is simple algebra except one theorem of Mazur.
ER -