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 | 4 |
| 3 | 17 |
| 4 | 87 |
| 5 | 490 |
| 6 | 2945 |
| 7 | 18517 |
| 8 | 120340 |
| 9 | 802005 |
| 10 | 5451651 |
| 11 | 37652546 |
| 12 | 263480357 |
| 13 | 1864065017 |
| 14 | 13311094644 |
| 15 | 95816113129 |
| 16 | 694511157535 |
| 17 | 5064818563258 |
| 18 | 37135165923801 |
| 19 | 273581694291309 |
| 20 | 2024194855052180 |
| 21 | 15034769479254861 |