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 | 0 |
| 2 | 1 |
| 3 | 7 |
| 4 | 31 |
| 5 | 139 |
| 6 | 609 |
| 7 | 2677 |
| 8 | 11827 |
| 9 | 52648 |
| 10 | 236071 |
| 11 | 1065774 |
| 12 | 4841428 |
| 13 | 22115678 |
| 14 | 101531221 |
| 15 | 468224323 |
| 16 | 2168076055 |
| 17 | 10076177264 |
| 18 | 46986612235 |
| 19 | 219777649588 |
| 20 | 1030892581741 |
| 21 | 4848039893338 |
| 22 | 22853638285655 |
| 23 | 107970202258065 |