Acronym day Name decayotton,9D simplex (α9),pyroyotton,enneazettal pyramid Circumradius sqrt(9/20) = 0.670820 Inradius sqrt(7/60) = 0.341565 Dual (selfdual, in different orientation) Confer general polytopal classes: simplex Externallinks

Incidence matrix according to Dynkin symbol

```x3o3o3o3o3o3o3o3o

. . . . . . . . . | 10 ♦  9 |  36 |  84 | 126 | 126 |  84 | 36 |  9
------------------+----+----+-----+-----+-----+-----+-----+----+---
x . . . . . . . . |  2 | 45 ♦   8 |  28 |  56 |  70 |  56 | 28 |  8
------------------+----+----+-----+-----+-----+-----+-----+----+---
x3o . . . . . . . |  3 |  3 | 120 ♦   7 |  21 |  35 |  35 | 21 |  7
------------------+----+----+-----+-----+-----+-----+-----+----+---
x3o3o . . . . . . ♦  4 |  6 |   4 | 210 ♦   6 |  15 |  20 | 15 |  6
------------------+----+----+-----+-----+-----+-----+-----+----+---
x3o3o3o . . . . . ♦  5 | 10 |  10 |   5 | 252 ♦   5 |  10 | 10 |  5
------------------+----+----+-----+-----+-----+-----+-----+----+---
x3o3o3o3o . . . . ♦  6 | 15 |  20 |  15 |   6 | 210 ♦   4 |  6 |  4
------------------+----+----+-----+-----+-----+-----+-----+----+---
x3o3o3o3o3o . . . ♦  7 | 21 |  35 |  35 |  21 |   7 | 120 |  3 |  3
------------------+----+----+-----+-----+-----+-----+-----+----+---
x3o3o3o3o3o3o . . ♦  8 | 28 |  56 |  70 |  56 |  28 |   8 | 45 |  2
------------------+----+----+-----+-----+-----+-----+-----+----+---
x3o3o3o3o3o3o3o . ♦  9 | 36 |  84 | 126 | 126 |  84 |  36 |  9 | 10
```

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