This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 3 |
| 5 | 4 |
| 6 | 20 |
| 7 | 24 |
| 8 | 192 |
| 9 | 280 |
| 10 | 2800 |
| 11 | 17280 |
| 12 | 61600 |
| 13 | 207360 |
| 14 | 1976832 |
| 15 | 28028000 |
| 16 | 448448000 |
| 17 | 696729600 |
| 18 | 3811808000 |
| 19 | 12541132800 |
| 20 | 250822656000 |
| 21 | 5069704640000 |
| 22 | 111533502080000 |
| 23 | 115880067072000 |
| 24 | 2781121609728000 |
| 25 | 21277380032004096 |
| 26 | 447206762741760000 |