A Regular Rep Icosahedron of Order Four

Can a net of a regular icosahedron be cut into smaller polygons, each of which is itself a net of a regular icosahedron? Nomi, Shiota, Kamata and Uehara explicitly recorded this existence question in 2025. We give an affirmative answer with four equal-area pieces. The outer net is a polyiamond of eighty unit equilateral triangles and folds to an icosahedron of edge length 2; each twenty-triangle piece is an edge net of one of edge length 1. Two noncongruent small-net shapes occur twice each. The search uses a half-turn of the subdivided icosahedron to find a surface cover, followed by a separate search for a compatible planar development. We present the exact construction and a standalone verifier that checks geometry, topology and every folding identification using integer arithmetic.

Authors

Publication Details

Journal
Zenodo (CERN European Organization for Nuclear Research)
Published
2026-10-29
DOI
https://doi.org/10.5281/zenodo.23750175
Primary Topic
Mathematics and Applications
Type
preprint
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preprint

A Regular Rep Icosahedron of Order Four

John Seamons
Zenodo (CERN European Organization for Nuclear Research)
Mathematics and Applications
preprint

A Regular Rep Icosahedron of Order Four

John Seamons
preprint en

Abstract

Can a net of a regular icosahedron be cut into smaller polygons, each of which is itself a net of a regular icosahedron? Nomi, Shiota, Kamata and Uehara explicitly recorded this existence question in 2025. We give an affirmative answer with four equal-area pieces. The outer net is a polyiamond of eighty unit equilateral triangles and folds to an icosahedron of edge length 2; each twenty-triangle piece is an edge net of one of edge length 1. Two noncongruent small-net shapes occur twice each. The search uses a half-turn of the subdivided icosahedron to find a surface cover, followed by a separate search for a compatible planar development. We present the exact construction and a standalone verifier that checks geometry, topology and every folding identification using integer arithmetic.

Zenodo (CERN European Organization for Nuclear Research)
Mathematics and Applications
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