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) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 0 |
| 8 | 0 |
| 9 | 1 |
| 10 | 1 |
| 11 | 15 |
| 12 | 15 |
| 13 | 140 |
| 14 | 140 |
| 15 | 1050 |
| 16 | 1050 |
| 17 | 6951 |
| 18 | 6951 |
| 19 | 42525 |
| 20 | 42525 |
| 21 | 246730 |
| 22 | 246730 |
| 23 | 1379400 |
| 24 | 1379400 |
| 25 | 7508501 |
| 26 | 7508501 |
| 27 | 40075035 |
| 28 | 40075035 |
| 29 | 210766920 |
| 30 | 210766920 |
| 31 | 1096190550 |