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 | 1 |
| 3 | 5 |
| 4 | 23 |
| 5 | 155 |
| 6 | 1236 |
| 7 | 11286 |
| 8 | 116333 |
| 9 | 1329433 |
| 10 | 16630343 |
| 11 | 225606826 |
| 12 | 3294976854 |
| 13 | 51496560764 |
| 14 | 856858516809 |
| 15 | 15112857079891 |
| 16 | 281479726839851 |
| 17 | 5517842789917283 |
| 18 | 113510479973132860 |
| 19 | 2444032094604379100 |
| 20 | 54948814775692303024 |
| 21 | 1287258966133883349701 |