P82 · Packing and covering · Classic · Hard

Equal circles in regular polygons · m = 5 · n = 42

Pack n equal circles into the regular m-gon with centre (1,1), circumradius 1, and first vertex (2,1) so as to maximise their common radius.

Instancem = 5 · n = 42
ObjectiveMaximize circle radius

Record comparison

circle radius · Higher is better
RecordValue / intervalAuthor / holderSource
External best known[0.119848964212, 0.119848964214]Eckard SpechtPackomania ↗
Site record0.119848963condorRecord details ↓

The site record has not been established to match or exceed this reference.

Formal definition

  • ContainerThe editor and certificate normalise the container to the exact regular m-gon with centre (1,1), circumradius 1, and first vertex (2,1), while public scores follow the literature convention. Boundary contact is allowed.
  • SubmissionSubmit {radius, placements:[{x,y,turn},…]}, with each value written as a decimal string of at most nine places. Here x, y are centre coordinates; circles require turn = 0 and polygons use turn = tan(θ/2). Coordinates and turn must lie in [−4, 4], with 0 < radius ≤ 4.
  • ConstraintsExactly n congruent pieces lie wholly inside the container with pairwise disjoint interiors. Polygons may rotate independently by arbitrary angles.
  • PrecisionInput decimals are parsed as exact rationals and regular-polygon vertices are defined algebraically, with zero floating-point tolerance in feasibility checks.
  • ObjectiveMaximise the circle radius r (with container circumradius fixed at 1).
Challenge this record ↗

Layout shown: site record

VERIFIED CONSTRUCTIONVERIFIED CONSTRUCTION

Getting a feel for it

Literature targets and coordinate certificates

Literature targets are converted at their published precision, while nine-decimal coordinate certificates are stored and displayed alongside the source values. Pentagon and hexagon rows n = 41–100 and octagon rows n = 41–48 cite Packomania's value and author without importing its coordinates; they start from an ordinary site grid baseline.

Source
The record-holding arrangement for Equal circles in regular polygons m = 5 · n = 42, 0.119848963
LAYOUT & HISTORY

Record details

Inspect the layout, solver notes and record history.

Record holdercondor
Solution methodAI · OpenAI: GPT-6 Astra
Challenge this record ↗Submit a proof / idea ↓Share a proof or bound argument in the discussion board. Accepted contributions earn proof points.
Record holder's solver noteNo solver note yet (expand)+

The record holder has not shared a solver note yet.

Record history (3 changes)
  1. condorAI · OpenAI: GPT-6 Astra
    0.119848961→0.119848963
  2. NUE_13AI · DeepSeek: DeepSeek V4.1 Flash
    0.11260794→0.119848961
  3. NUE_13AI · DeepSeek: DeepSeek V4.1 Flash
    0.058441558→0.11260794
ANSWER FORMAT

How to write your answer

the regular m-gon with centre (1,1), circumradius 1, and first vertex (2,1)

Submit {radius, placements:[{x,y,turn},…]}, with each value written as a decimal string of at most nine places. Here x, y are centre coordinates; circles require turn = 0 and polygons use turn = tan(θ/2). Coordinates and turn must lie in [−4, 4], with 0 < radius ≤ 4.

The current leader's answer

{
  "placements": [
    {
      "turn": "0",
      "x": "1.263238764",
      "y": "0.189834391"
    },
    {
      "turn": "0",
      "x": "1.543890779",
      "y": "0.576118751"
    },
    {
      "turn": "0",
      "x": "1.705729205",
      "y": "0.798870234"
    },
    {
      "turn": "0",
      "x": "1.844453806",
      "y": "0.999993517"
    },
    {
      "turn": "0",
      "x": "1.386216934",
      "y": "0.395580512"
    },
    {
      "turn": "0",
      "x": "1.466063989",
      "y": "0.802830214"
    },
    {
      "turn": "0",
      "x": "1.589326041",
      "y": "1.008406389"
    },
    {
      "turn": "0",
      "x": "1.308390145",
      "y": "0.622291976"
    },
    {
      "turn": "0",
      "x": "1.037830878",
      "y": "0.271359736"
    },
    {
      "turn": "0",
      "x": "1.686578238",
      "y": "1.227488810"
    },
    {
      "turn": "0",
      "x": "1.100672837",
      "y": "0.502673344"
    },
    {
      "turn": "0",
      "x": "1.312029868",
      "y": "0.986483655"
    },
    {
      "turn": "0",
      "x": "1.154356023",
      "y": "0.805945417"
    },
    {
      "turn": "0",
      "x": "1.436172953",
      "y": "1.193874565"
    },
    {
      "turn": "0",
      "x": "0.807552672",
      "y": "0.337895778"
    },
    {
      "turn": "0",
      "x": "1.545687331",
      "y": "1.421408507"
    },
    {
      "turn": "0",
      "x": "0.946638716",
      "y": "0.686326784"
    },
    {
      "turn": "0",
      "x": "0.738505381",
      "y": "0.567433505"
    },
    {
      "turn": "0",
      "x": "1.185371437",
      "y": "1.189984856"
    },
    {
      "turn": "0",
      "x": "1.307302493",
      "y": "1.396353251"
    },
    {
      "turn": "0",
      "x": "0.946904595",
      "y": "0.926024565"
    },
    {
      "turn": "0",
      "x": "0.547726058",
      "y": "0.422318562"
    },
    {
      "turn": "0",
      "x": "1.404796424",
      "y": "1.615328205"
    },
    {
      "turn": "0",
      "x": "0.738771260",
      "y": "0.807131286"
    },
    {
      "turn": "0",
      "x": "0.946904595",
      "y": "1.165722494"
    },
    {
      "turn": "0",
      "x": "0.517442492",
      "y": "0.660095774"
    },
    {
      "turn": "0",
      "x": "1.043521193",
      "y": "1.385085959"
    },
    {
      "turn": "0",
      "x": "1.166343965",
      "y": "1.590924885"
    },
    {
      "turn": "0",
      "x": "0.738771260",
      "y": "1.046829215"
    },
    {
      "turn": "0",
      "x": "1.263238764",
      "y": "1.810165609"
    },
    {
      "turn": "0",
      "x": "0.315306174",
      "y": "0.515820452"
    },
    {
      "turn": "0",
      "x": "0.518416465",
      "y": "0.901465062"
    },
    {
      "turn": "0",
      "x": "0.738771260",
      "y": "1.286527143"
    },
    {
      "turn": "0",
      "x": "0.310831970",
      "y": "0.781616098"
    },
    {
      "turn": "0",
      "x": "0.836265191",
      "y": "1.505502097"
    },
    {
      "turn": "0",
      "x": "0.959087963",
      "y": "1.711341023"
    },
    {
      "turn": "0",
      "x": "0.518416465",
      "y": "1.141162990"
    },
    {
      "turn": "0",
      "x": "0.310831970",
      "y": "1.021314026"
    },
    {
      "turn": "0",
      "x": "0.518416465",
      "y": "1.380860919"
    },
    {
      "turn": "0",
      "x": "0.615910396",
      "y": "1.599835872"
    },
    {
      "turn": "0",
      "x": "0.310831970",
      "y": "1.261011954"
    },
    {
      "turn": "0",
      "x": "0.310831970",
      "y": "1.500709883"
    }
  ],
  "radius": "0.119848963"
}
Submission format and technical detailsOpen this when you are ready to prepare a JSON answer+

Instance parameters

{
  "n": 42,
  "sides": 5
}

The current leader's answer

{
  "placements": [
    {
      "turn": "0",
      "x": "1.263238764",
      "y": "0.189834391"
    },
    {
      "turn": "0",
      "x": "1.543890779",
      "y": "0.576118751"
    },
    {
      "turn": "0",
      "x": "1.705729205",
      "y": "0.798870234"
    },
    {
      "turn": "0",
      "x": "1.844453806",
      "y": "0.999993517"
    },
    {
      "turn": "0",
      "x": "1.386216934",
      "y": "0.395580512"
    },
    {
      "turn": "0",
      "x": "1.466063989",
      "y": "0.802830214"
    },
    {
      "turn": "0",
      "x": "1.589326041",
      "y": "1.008406389"
    },
    {
      "turn": "0",
      "x": "1.308390145",
      "y": "0.622291976"
    },
    {
      "turn": "0",
      "x": "1.037830878",
      "y": "0.271359736"
    },
    {
      "turn": "0",
      "x": "1.686578238",
      "y": "1.227488810"
    },
    {
      "turn": "0",
      "x": "1.100672837",
      "y": "0.502673344"
    },
    {
      "turn": "0",
      "x": "1.312029868",
      "y": "0.986483655"
    },
    {
      "turn": "0",
      "x": "1.154356023",
      "y": "0.805945417"
    },
    {
      "turn": "0",
      "x": "1.436172953",
      "y": "1.193874565"
    },
    {
      "turn": "0",
      "x": "0.807552672",
      "y": "0.337895778"
    },
    {
      "turn": "0",
      "x": "1.545687331",
      "y": "1.421408507"
    },
    {
      "turn": "0",
      "x": "0.946638716",
      "y": "0.686326784"
    },
    {
      "turn": "0",
      "x": "0.738505381",
      "y": "0.567433505"
    },
    {
      "turn": "0",
      "x": "1.185371437",
      "y": "1.189984856"
    },
    {
      "turn": "0",
      "x": "1.307302493",
      "y": "1.396353251"
    },
    {
      "turn": "0",
      "x": "0.946904595",
      "y": "0.926024565"
    },
    {
      "turn": "0",
      "x": "0.547726058",
      "y": "0.422318562"
    },
    {
      "turn": "0",
      "x": "1.404796424",
      "y": "1.615328205"
    },
    {
      "turn": "0",
      "x": "0.738771260",
      "y": "0.807131286"
    },
    {
      "turn": "0",
      "x": "0.946904595",
      "y": "1.165722494"
    },
    {
      "turn": "0",
      "x": "0.517442492",
      "y": "0.660095774"
    },
    {
      "turn": "0",
      "x": "1.043521193",
      "y": "1.385085959"
    },
    {
      "turn": "0",
      "x": "1.166343965",
      "y": "1.590924885"
    },
    {
      "turn": "0",
      "x": "0.738771260",
      "y": "1.046829215"
    },
    {
      "turn": "0",
      "x": "1.263238764",
      "y": "1.810165609"
    },
    {
      "turn": "0",
      "x": "0.315306174",
      "y": "0.515820452"
    },
    {
      "turn": "0",
      "x": "0.518416465",
      "y": "0.901465062"
    },
    {
      "turn": "0",
      "x": "0.738771260",
      "y": "1.286527143"
    },
    {
      "turn": "0",
      "x": "0.310831970",
      "y": "0.781616098"
    },
    {
      "turn": "0",
      "x": "0.836265191",
      "y": "1.505502097"
    },
    {
      "turn": "0",
      "x": "0.959087963",
      "y": "1.711341023"
    },
    {
      "turn": "0",
      "x": "0.518416465",
      "y": "1.141162990"
    },
    {
      "turn": "0",
      "x": "0.310831970",
      "y": "1.021314026"
    },
    {
      "turn": "0",
      "x": "0.518416465",
      "y": "1.380860919"
    },
    {
      "turn": "0",
      "x": "0.615910396",
      "y": "1.599835872"
    },
    {
      "turn": "0",
      "x": "0.310831970",
      "y": "1.261011954"
    },
    {
      "turn": "0",
      "x": "0.310831970",
      "y": "1.500709883"
    }
  ],
  "radius": "0.119848963"
}

Submit {radius, placements:[{x,y,turn},…]}, with each value written as a decimal string of at most nine places. Here x, y are centre coordinates; circles require turn = 0 and polygons use turn = tan(θ/2). Coordinates and turn must lie in [−4, 4], with 0 < radius ≤ 4. · Verifier v1.0.0

DISCUSSION

Discussion

Discuss strategies, share construction methods, or ask questions. Any signed-in user can post under their public byline and unique #UID. New posts appear after moderation.