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 | 1 |
| 2 | 3 |
| 3 | 16 |
| 4 | 122 |
| 5 | 1208 |
| 6 | 14704 |
| 7 | 212336 |
| 8 | 3547984 |
| 9 | 67337728 |
| 10 | 1430990976 |
| 11 | 33664165632 |
| 12 | 868592478720 |
| 13 | 24390846882816 |
| 14 | 740570519159808 |
| 15 | 24177326011834368 |
| 16 | 844599686386919424 |
| 17 | 31438092340685144064 |
| 18 | 1242230898248798896128 |
| 19 | 51933512200489564962816 |
| 20 | 2290351520336982559358976 |