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 | 0 |
| 1 | 2 |
| 2 | 12 |
| 3 | 69 |
| 4 | 392 |
| 5 | 2235 |
| 6 | 12804 |
| 7 | 73710 |
| 8 | 426192 |
| 9 | 2473704 |
| 10 | 14405800 |
| 11 | 84137130 |
| 12 | 492652824 |
| 13 | 2891110235 |
| 14 | 16999928820 |
| 15 | 100136858625 |
| 16 | 590778928800 |
| 17 | 3490370847876 |
| 18 | 20647839813048 |
| 19 | 122287764072938 |
| 20 | 725023671281520 |
| 21 | 4302720916638417 |